I do a nice black bean turkey chilli that keeps well. You can reheat it in a crockpot. It is low cal but very flavorful from spices, coffee, cocoa, chiles and vinegar. If you are interested let me know. You can serve it in little bowls, or coffee mugs, even heat proof disposables. I made it recently for a lunch for 25 and got quite a lot of compliments.

You can also cook a layered chicken enchilada casserole dish with either red or green sauce and just reheat.

What about a paella that you can just reheat the next day?

I'd say orange-flavoured couscous with dried fruit and nuts. Cook couscous as you would normally. Then remove from heat and add toasted flaked almonds, toasted and roughly crushed cumin and coriander seeds, orange zest and orange juice, dried mint, dried fruit (I love dried cherries and currants). Toss together and let sit overnight in fridge - you can add some chopped chicken if you like. Next morning, warm up, add some more fresh orange (not from a bottle). To serve, have a bowl of chopped coriander/cilantro leaves and chopped parsley

More good ideas. Can't thank you all enough.

Carbonnades a la flamande. http://kayatthekeyboard.wordpress.com/2009/02/28/read-the-recipe-thoroughly-first-dummy-or-beef-onion-beer-stew-on-a-snowy-day/
You can make it the night before, toss it all in the crock pot, and let it simmer all morning. Also, if you have a few minutes in the kitchen before lunch, you can up some egg noodles really quickly to serve it over.

I'm a big fan of savory bread puddings for this type of thing, as well as saucy meatballs (either in a tomato-based sauce or a rich mushroom sauce). The suggestions above sound great, too!

Julia's Ratatouille

Julia Child's ratatouille is so delicious, and actually improves in flavor with an overnight in the refrigerator. You can easily heat it up on the stove top. Double the recipe for 12 servings. There is a PDF of her original recipe online.

Try - http://www.food52.com/recipes/7403_israeli_couscous_with_squash_dried_cherries_pistachios

wonderful at room temp.

Great ideas, everyone. Thanks so much. Gives me something to chew on (pun intended).

Pulled pork!

One of my co-workers recently brought in home-made stromboli and everyone ate it like it was their last meal.

My co-workers often swedish meatballs and allow them to heat in a crockpot until lunch, also chili, nacho cheese (eew), and Pho broth (with all the inclusions to the side to add yourself), but not as often.
I almost always bring pie.

Chicken and dumplings. You can make it the night before, toss it into your crock-pot and the next day take it to work and plug it in. I know, it is really simply and not the prettiest presentation but it has the advantage being easy and will be thoroughly enjoy it. Seriously. I've served this at bring-a-plate to all sorts different people and I've never had leftovers.

Crockpot dishes that I can think of off the top of my head are: Chili (great in a crockpot) beef stew, any kind of hearty soup, chicken with 40 cloves of garlic (just double most standard recipes)