Love lentils! One way that I fix them is to make a soup/stew using lentils and barley (or brown rice). Add onion, garlic, veggie stock (or chicken), a bit of celery, carrot....a very filling meal!
With red lentils I make a curry using sweet potatoes as well. Fry up some onion, ginger, and garlic, with various spices (cumin, turmeric, curry, etc). Add lentils and water(or stock). Let that simmer for about 15 minutes then add peeled and chopped sweet potato. Simmer till sweet potato is cooked.