The best selection of lentils I have seen around where I live (West Chester, PA area) is at:
Himalayan Indian Grocery (610) 524-3100 29 Marchwood Rd, Exton, PA
They also have a small produce section that is ridiculously cheap.
Might be a little far for you to travel, but it's currently my favorite place for groceries. There is also a great Asian Market within the same shopping center.