Casserole Recipes

I've realised that there's a bad hole in my cookery knowledge - I've never cooked a Casserole. I know that many of you know quite a lot about cooking Casseroles so if you were willing to share and recipes/advice I would be very greatful. I can't eat potatoes but I can just substitute sweet potato or swede or similar.

I'm first thinking of making Lamb and Mushroom Casserole so any advice relating to that would be especially welcome.