A friend of mine served cold poached salmon with a dill-yogurt sauce at a small dinner party-- it was delicious! Another plus: even though I showed up early, she wasn't running around finishing dinner, because the salmon had been poached ahead of time and was resting in the refrigerator when the guests arrived!
Sorry that I don't have a recipe, but maybe that will at least give a little inspiration.

I LOVE this idea! What about a cold grain dish - wild rice or quinoa. Or a cold pasta dish.

I'm a big fan of cold noodles (think peanut noodles/sesame noodles with veggies). Pretty much every salad you can find at a deli (tuna, egg, chicken, potato, coleslaw) tastes great cold. Roasted veggies actually taste pretty great cold, too.

I'd say go for a quiche. Sandwiches are also winners, although a bit casual.

Cold yogurt soup is delicious, and it's better the next day:

http://www.foodandwine.com/recipes/cold-cucumber-and-yogurt-soup-with-dill

I made the 'peppery whole wheat pasta with wilted chard' the other week. It was pretty great, we ate it straight from the fridge.
http://www.thekitchn.com/thekitchn/pasta/dinnertolunch-recipe-peppery-whole-wheat-pasta-with-wilted-chard-113975?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A apartmenttherapy%2Fthekitchn %28The Kitchn%29&utm_content=Google Reader

Or would your friends eat a big delicious salad? Maybe with a scoop of chicken/tuna salad on top?

Tortellini salad! (80's flashback) Toss cooled cooked tortellini with sundried tomatoes, salami, mozzerella, basil, and a nice vinagrette---your own or bottled.
Pesto or curried chicken salad on mini pitas.
Gazpacho---spicy vegetable or minted fruit.
Have a cool house cooling! Love the idea.

Naenmyeun - Korean cold buckwheat noodle soup served with rare steak, hard boiled eggs, and cucumber on top. It's a great summer party dish!

Hey, a Salade Niçoise is quite filling, everybody picks what they like, it's cold and one of my favorite.

I would strongly suggest Laura Calder Salade Niçoise http://www.foodnetwork.ca/recipes/Appetizer/Fish/recipe.html?dishid=9054

The vinaigrette is to die for (terragon yum) and if you serve tuna (being from a can or fresh) with good quality olive oil and lemon, plus some cold potatoes, it's very good.

And you can prepare in advance if you don't put the dressing on too early.

Plus it's lighter than mayo type based salads.

Can I say anything else?

Hopefully these would all be simple and quick.

- quiche (really good if homemade)
- tart (mushroom, leek/onion, cheese)
-pasta salad (any kind)
- sandwiches (any kind)

How about pizza? Ice cream for dessert!

You can make some fancy sandwiches, with the right ingredients and presentation. My friend takes whole loaves of ciabatta, then layers on beautiful ingredients, and then cuts it into manageable pieces, and lays them on a nicely decorated platter. She always makes one veggie. It's so lovely.

Slightly off-topic but when my parents had their "mortgage-burning" party we decided it should be a "house-cooling" party. Rather than having guests bring presents, we wrapped up various items from the house (nice household decor items that we no longer needed) and gave them away as parting gifts.

I have never considered eating quiche cold. The idea of cold eggs makes me all squiggy... (no, I don't eat tamago either). Quiche is a warm dish in my book.

The cold salmon sounds like a great dish. The flavor is strong enough not to get lost when its cold, it can actually mellow it a bit.

A salad or salad bar also sound like great ideas.

Bahn Mi or other types of out of the ordinary sandwiches? (okay bahn mi aren't exactly new, but not everybody has eaten/heard of them and they could be an exotic choice for being made at home.

Cold roast chicken! Makes me think of Hemingway.

Another buttermilk/kefir soup:

- Mix together chopped vegetables: Tomato, paprika, cucumber, radish. (You can experiment with adding maize/corn or lightly steamed broccoli, lightly steamed carrots, peas, apples, maybe some green onions or leek etc.)
- Season the vegetable mix with salt and you may let it sit for 5 minutes or so
- Add chopped fresh(or dried) basil and/or oregano.
- Pour some buttermilk into the mix, enough for the mix to be less dry than regular salad and mix. I'd say you could use plain yoghurt if it's not too thick but I haven't tried it myself.
- Cube a few loaves of bread and fry/toast them in butter until crispy. I usually use black rhye bread but I'd say any other would do too. The black bread is less fluffy than others and has a crispy crusp which I usually leave on because it also adds some crunchy texture and gets soggy less quickly. Though I guess you could use garlic bread or some other roasted/toasted versions of bread.

Serve placing the bread cubes onto the plate & the salad/soup mixture over them. Eat immediately otherwise the bread will turn soggy and that's not so nice anymore.

casserole. bake it, chill it, eat it. done.

um, sandwiches, Jade. Put out an awesome deli spread with different buns and bread, good cheese, and things like marinated artichoke hearts and spicy eggplant. Invite me.