Yesterday I made curried lentils with dinner (recipe from The Colour Book of Indian Cooking edited by Eileen Turner). I also make a lentil curry based on the Lentils and Rice recipe in Saving Dinner by Leanne Ely. The two recipes are very different, but both good, and the one I make will depend on my mood at the time.
I am very fond of lentils. Mujaddara, a dish of lentils and rice, is believed to be the "mess of pottage" that Esau sold his birthright for. I'm still on the lookout for the perfect mujaddara recipe.
My favorite lentil soup recipe is from Marcella Hazan's Essentials of Classic Italian Cooking. I've tried a few others, but I think I'll stick with this one.