Lavender, basil, onions, rosemary, leaf lettuce grows incredibly fast, any type of mint is very fast growing and smells wonderful when you walk by it.
Overall though, a lot of spices can be grown indoors quite easily. Bamboo can grow pretty good if you have the right environment. Bean sprouts are pretty easy as well.
You can grow all kind nof useful things. And many things are useful to different people for different reasons lol.
I have a lot of spinning(wool/fibre) friends that grow plants indoors for dyes which is pretty cool because plants don't dye the way you'd think they would. It's fun to play around with :]