Meatloaf!
Roasted Chicken (just read the post "A Million ways to Roast a CHicken)
Fruit Salad (always refreshing).
I make a kale dish that wilts the kale in bacon grease (barely a tablespoon), after wilted add stewed tomatoes and crumbled bacon -can also add shallots and garlic.
creamed spinach, creamed peas (add shredded swiss cheese)

I think ouefs vert-pre (eggs with potatoes and greens) would work well if you could reheat it a little before serving. Or a savoury squash bread pudding, perhaps.

Any kind of grain salad - that's what I usually bring to our friend potlucks. I always leave with my container empty. Here's my current fave--quinoa with roasted tomatoes, avocado, and pesto.

I made broccoli cheese twice baked potatoes for a potluck a few weeks ago. They were a big hit. I did most of the prep ahead of time and then just heated them in the oven. Easy to feed a crowd with just a few simple ingredients.

Salads beyond lettuce, onions and tomatoes are always great.

Also, noodles!

(I don't consider noodles to be pasta.)

Don't know if you'd consider this a casserole, but I made (veganized) this recently and it was wildly popular and delicious. Even good room temp.
http://www.myrecipes.com/recipe/upside-down-salsa-cornbread-00420000010119/

Also, homemade pizza! You could put a few different kinds together, or set out the toppings and let people make their own on pitas or rice tortillas. It's fun and interactive. Maybe a prize for the most creative toppings combo?

Big pots of soup! Easy to put together, loads of flavor and nutrition, travel well in a crockpot. I'm a fan of lentil soups--so versatile. As the weather warms you could also do gazpacho.

Have a breakfast-for-dinner potluck! Something a little different, and who doesn't like breakfast for dinner? :)

Giant fruit salad. Everything fresh and colorful under the sun. Toss with some nuts and a savory dressing for an entree.

My favorite is Cowboy Ciao's Salad. It's visually stunning, really unique and sooo delicous. Rows of arugula, dried corn, basil & tomato, couscous, pepitas, asiago, and dried currants. Recipe here http://www.loveumadly.com/2011/09/ciao-baby/

The curried quinoa salad with mango and black beans from Dinner with Julie (http://dinnerwithjulie.com/2010/03/29/curried-quinoa-salad-mango/). It's easy to make, delicious and portable!

I do this pretty regularly too. I love to cook a roast (chicken, turkey, duck, whole fish, beef or pork) with potatoes and make gravy from the drippings. Other mains: goat cheese rounds in marinara sauce (serve with bread), bean soups (they're thick and versatile enough to be modified for your crowd), labneh, zatar & pickles (served with fresh flat bread), stir fries (my fav's beef & broccoli), a pot of meatballs (or chicken balls, or veggie balls) with gravy.

Some big hits that I've had:

Three-bean salad, corn pudding, taco salad (pulled from a 1950's church cookbook!), roasted pearl onions and mushrooms (great for restricted diets), and Derby pie. I also find that gatherings usually have precious few vegetables, and people seem SO thankful when you bring them. And I don't mean green bean casserole or a salad pre-drenched with dressing. Bring what YOU like to eat!

This big beautiful salad with lentils, rice, spinach, roasted beets and olives feeds a lot of people and is satisfying and very pretty!

I'm a big fan of large savory pies. The empanda gallega is lovely, and feeds a lot of people. Here's a vegetarian version.

Or try this chard, pistachio and golden raisin tart. It's big and pretty, you can cut it into as many slices as you need, and it's delicious!

If this is a regular thing, you should pick up a good slow cooker cookbook, all those recipes are designed to feed a crowd. I really like Cooks Illustrated slow cooker revolution, initially most of the recipes seem a little fussy but I have a slow cooker with a stovetop safe insert so I can cook all in the same pan.

Raw vegetable salads and slaws, cooked veggie salads (like potato salad with green beans and vinaigrette), room temp roasted veggies tossed in oil and vinegar, gratineed vegetables (if you have access to an oven or can keep them hot), and trays of fresh and/or pickled vegetables with at least one kind of dip are all always popular. I completely agree with @Esotericara - potlucks are usually way under-vegetabled and fresh and healthy foods generally go over rather well.

Fresh fruit salads are also wonderful. Oranges with red onions and honey mustard vinaigrette, strawberries and grapefruit, stone fruit in lemon yogurt dressing, etc. They are deliciously sweet without being as heavy as dessert. I find that sweet vinaigrettes make them sprightly, instead of heavy like cool whip-based ones.

On a main-dish related note, tacos and soup are awesome, inexpensive, and will easily feed many people at once.

At the potlucks that I have been going to the last several years, what has been sorely missing is main dishes. Everyone seems to run to the grocery store and buy and assembled salads and plates of veggies and dip (same veggies, same dip, everywhere), so there are plenty of those.

So, I've made it a point to try to being something like a roasted stuffed turkey breast, a pork tonnato (which is a cold dish), a rolled stuffed meat loaf, or Martha Stewart's Pressed Picnic Sandwich (everyone loves that).

I've also brought Martha's Watermelon Gazpacho (very refreshing, and goes nicely with the pressed sandwich), Swiss potato salad (cooked in chicken bouillon, sliced thin and doused with white wine, and a dressing of olive oil, white balsamic, chopped capers and parsley), strawberry and pineapple salad (soft curly butter lettuce, and a dressing of poppy seeds, sesame seeds, apple cider vinegar, honey, and grapeseed oil), scalloped potatoes, marinated vegetables, salade nicoise. Also, lots of desserts -- Danish rice pudding (whipped cream folded in with the rice cooked in milk, served with a raspberry coulis); Eton Mess; Pavlova; flan; undercooked chocolate cake.

I almost always bring a Mango Black Bean salad. Its kind of a pain in the ass to bring something that needs to be reheated so it works well.

Baked sweet potatoes (peeled & cut in half). Never once been duplicated or had leftovers. What began as a desperate attempt to 'save the day' has now become a faithful standby

Warm potato and green bean salad with mustard/parmesan dressing. Boiled little or larger red potatoes, sliced in rounds, sliced radishes, blanched green beans. Mustart vinaigrette. After tossing everything (potatoes just slightly cooled), add 1/4 cup of grated parmesan over everything, it's a great combo of warm, crispy and tangy. I make it so it's 1:1 green beans to potatoes volume wise and 1/3 radishes.
A panzanella is always great, with whatever veg is in season. This one is from Smitten Kitchen (and those croutons are amazing by themselves too)
http://smittenkitchen.com/2008/04/spring-panzanella/

My usual go to for potlucks is my signature grilled romaine and broiled brussels sprouts

If you have main-course duty, "To-die-for crock pot roast"!
http://www.food.com/recipe/to-die-for-crock-pot-roast-27208
Even my foodie friends have claimed this to be the best pot roast they've ever eaten and it's SO INCREDIBLY EASY.