Spirits last a decent amount of time- Maybe some gin or bourbon, a few bottles of seltzer or tonic, a bottle of bitters, and limes and lemons. From there you have the makings for a gin rickey, and old fashioned, or just bourbon & soda or G&T. You could get a 6 pack of nice microbrew beer to keep in the fridge too.
On the food front I'd keep good cheese (or a cheese dip- whole food's premade stuff like feta salsa and pimento cheese always get a good reception when I have friends over), crackers, nuts, and berries (they do go bad but you can always snack on them yourself).

Chips and salsa are good summer time snacks too.

I always have this problem with beverages. My husband and I pretty much only drink water, and while we usually have a few beers cold & wine around, we never have anything non-alcoholic to offer guests.

My favorite thing to have on hand is chickpea flour to make Socca. It is extremely easy to make, consists of solely pantry ingredients, and seems impressive. Also beer, wine, and scotch.

Here is Bittman's recipe:
http://query.nytimes.com/gst/fullpage.html?res=9E05E6D7153FF93AA25753C1A9639C8B63

Good cheese, berries, crackers, cheese honey, decadent ice cream/pudding, beer, sparkling wine, cab, bourbon, ice, olives, good bread, good evoo and sherry vinegar . . .

I have to second the cheese berries and crackers idea. Some good beer, a bottle of wine. Light things that you can pick up with your fingers and eat.

Dont forget eggs, bacons, and some scones for the next morning ;) lol.

Cheese, crackers, salami/jamon serrano/prosciutto, raw or roasted nuts, dried fruits, a bar of nice dark chocolate, maybe some fresh fruits like apples or pears that go well with cheese. You can quickly assemble a nice snacking platter with these items and even a picky guest is likely to enjoy at least some of those foods. On the drink front you could get some kind of fancy flavored syrup and keep seltzer on hand to make a quick non-alcoholic special drink. Since you don't drink soda normally, buy CANS of seltzer, tonic water, or soda so you only need to open them as you use them, if you have a whole bottle it will probably go flat before you finish it. You can keep the cans in the pantry and just pop a few in the fridge if you're expecting company.

Get yourself a soda-stream and make seltzer whenever you want :) It doesn't take much to flavor it, and you don't even have to use the syrup they sell. Just make some carbonated water, throw in some citrus juice, and voila! Refreshments.

@mrstiffsmith I have a few non-drinking friends and I like to keep some decaf tea, and cans of ginger beer (non-alcoholic, despite it's name) around. Lemonata is another good option. They can be used as mixers as well (ginger beer plus lime plays well with dark rum, gin, bourbon, or vodka; and I love lemonata mixed with either red wine or champagne and some berries to garnish), but feel special on their own or, in the case of the ginger beer, with a twist of lime.

I agree with all of the antipasto things - meats, cheeses, olives. And definitely eggs and breakfast items for a cheeky morning brunch!

Breakfast is what kept me coming back to my new sweetie's house... Nothing quite so endearing as a man getting up earlier than he has to, to fry bacon and butter toast for you. Stock up on good bread, jam, and butter, farm-fresh eggs, and fresh fruit. (and great bacon/sausage if the new snookums eats meat!)

For the cooler months, I love to have a cider mulling spices close at hand (and some apple juice and/or brandy) as well as good loose-leaf teas. It's very relaxing and cozy to sit on the couch and chat with warm drinks in hand.

I love the antipasto ideas people have suggested -- meats, cheeses, olives, nuts, fruit, crackers, wine, etc.

If you keep flour, butter, and cheddar cheese in your fridge, you can whip up a quick batch of cheese straws on short notice, and they're a very simple yet impressive snack.

http://homesicktexan.blogspot.com/2008/12/grasping-at-cheese-straws.html

If you keep a bag of arugula and have some prosciutto, I love this simple appetizer (from The Kitchn obviously)

http://www.thekitchn.com/lastminute-appetizer-prosciutt-132831

You could keep a block of cream cheese and a jar of chutney or preserves. Pour chutney/preserves over cream cheese block and then slice of hunks to spread on crackers.

for drink drinks i buy the small single size club soda and gingerale because i can never finish a whole big bottle before it goes flat. Then have a decent collection of spirits that people can mix with them. A box of wine in the fridge (which i enjoy myself) and a 6 pack of beer and you are set. Almost always have a 6 pack of sprite, coke and OJ as well as instant coffee and tea. It may all seem like a lot but one 6 pack of each will last you a surprisingly long time for the occasional guest. Just keep one of each in the fridge and a full ice tray in the freezer and you are set.

for snacks i have to throw out pita chips (or veggies) and hummus. Whole foods sells a bulk dehydrated hummus that is surprisingly good - i favor this because you can whip up a batch as needed because i always feel weird serving guests from the half eaten container I have been dipping out of for snacks.

In addition to the great suggestions so far, I'd say:

I like to keep a small pitcher of cucumber water during the summer months. It's a good way to make sure you stay hydrated if you're going out for an evening of drinks and makes a pretty accompaniment to whatever alcohol you're serving.

Plain Greek yogurt is pretty flexible. It's great for breakfast, or in the evening, throw in some fresh herbs and you've got a light dip for veggies or pita chips.

A loaf of sliced bread can keep well in the freezer for a long time so you're never without toast for breakfast.

Also keep a variety of breakfast beverages around. Some people only like one certain drink in the morning (coffee, decaf, black tea, chai, green tea, orange juice...), and it's really nice to be able to offer them what they would actually like to drink. Grab a few extra sugar packets the next time you get coffee, too -- some people might prefer to use Sweet n Low or raw sugar.

How about cookie dough? Who wouldn't like some freshly baked cookies?

Agree with Faith - a nice bottle of dry sherry and almonds is good to have around. Other antipasti such as Parma ham/jamon, smoked salmon, artichokes in olive oil, olives, a block of hard cheese such as Manchego or Parmesan. Some home-made pesto (you can freeze it until needed), pasta and green salad for an impromptu snack, in-season fruit, and chocolates. What more could one wish for?

Here in Texas, we have small BBQ joints practically around every corner. Try some smoked sausage from some place like that, plus some good crackers and cheese like others suggest.

since it's summer, i would make sure to keep fresh fruit in the house - especially fruit taht takes minimal prep (grapes, cherries, blueberries, strawberries, berries) but also any fruit that can easily be sliced. roasted nuts and of course, some cheese and crackers are always great! good luck!

If you're looking for a good non-alcoholic drink, I keep a bottle of berry nectar (a really thick juice) and mix it with soda water. It's a tasty Italian Soda type drink. I keep around cans of soda water and tonic so I don't have to worry about them going flat. For alcohol, I also keep some gin and limes around for G&T. And I have a bottle of Aperol in the fridge which is a great aperatif when mixed with soda and a squeeze of orange.

As far as make-ahead and freeze options....I have been using this recipe for goat cheese frittatas for about a month and my husband requests them EVERY morning. I added some bacon and chopped scallions to the recipe. Try serving them with toast, feta cheese, and fresh herbs (along with berries and a delicious cup of tea) and you will have a hearty breakfast that is very easy to pull together in the morning, especially after a late night out ;)

http://www.thekitchn.com/easy-breakfast-recipe-kale-and-goat-cheese-frittata-cups-166901

I usually keep a bottle of really good margarita mix in the fridge and have basic spirits. Also at least a bottle or wine and a few beers in the fridge (we like a few drinks, what can I say)

I'd disagree though about the sherry. I love sherry, but I have never had a friend or seen anyone but me or my mom who's down for drinking a little sherry here and there. Sign of the times I guess.

Crackers and things are always good. Chips and salsa or a good queso are always a hit with us. Anything I can literally dump in a bowl and let everyone go to town on. We're not big on setting up a cheese or charcuterie type plate usually. More fun snack type things. I'm a big baker so I'll throw something tasty in the oven quick if company comes over, but I know thats not the norm.

San Pellegrino water - we keep orange and lemon ones in the fridge for guests. They always think it's "fancy" and it's nicer than pop.

Good cheese and some grapes to go on the side with crackers, olives, mini pickles, tapenade, hummus or tzatziki with toasted pita, veggies and dip (chopped up and ready to go - carrots, celery, peppers, broccoli and cauliflower), a selection of good salami or other meats, goats cheese, arugula, salsa and guacamole.

We also keep lots of nuts on hand - homemade roasted almonds, pistachios and sunflower seeds.

Finally, we usually have a salad of some sort in the fridge (potato salad, pasta salad, potato pesto salad, green bean salad) and some leftovers (grilled steak or roast a chicken and tear it up - good for sandwiches, wraps or on top of a salad).

Good booze (wine, beer, whiskey), good music (jazz), good decadent food. The key is to make it look fancy but in reality it takes no effort.

One of my favs:
Put some chevre or goat cheese into a small bowl
Pour honey on cheese
Dip dried figs, apricots, nuts, whatever into cheese-honey mixture

I agree with the nuts...buy an assortment and keep them in the freezer, keeps them nice and fresh. Some good cured meats, they should last you a good while in the fridge also the dried fruits always goes well. Things that you can always have on hand and not worry too much about them going bad. That way all you would have to do is just pick up some good cheese if you want to. A safe all around crowd pleaser is a good aged cheddar!

I just keep a variety of candy and jerky in my nightstand: everyone loves a little post-coital snack.

From my personal experience, I ordered take-out lasagna from my favorite locally-owned Italian restaurant down the street, picked it up, and put it on plates for us. Lots fewer dishes, time, and worry (and I didn't try to pass it off as my own, either... I was honest! But I did tell him I wanted to introduce him to my favorite lasagna ever).

The next day he came over with a box of ingredients and baked me cookies in my own kitchen... and then cleaned everything up. Yeah, I've let him stick around. ;)