Mark's Daily Apple's Moroccan Chicken Casserole
Here's a Paleo Pot Pie recipe, which is pretty much a casserole
This breakfast casserole is a good one
Roasted Vegetable Ratatouille
I have a bunch of slow cooker/stew recipes, not as many one dish casserole recipes.
Fall Apart Pork Stew (This is a long cooked oven recipe, but could be thrown in crock pot)
Sausage & Butternut Squash Stew
Sweet Potato Beef Stew