Another indoor plant idea is sprouts. I usually do lentils, but you can sprout lots of stuff. The process I follow is simple -- soak them overnight, then dump them in a colander and cover with a damp handkerchief. Run water through it twice a day (to both rinse and keep damp). It typically takes 3 days or so. They're a great addition to salads, stirfries, etc.
Also, I'm not sure how well it would work indoors, but I really like katuk as a spinach replacement. It's a perennial, and even when I've lost them to freezes, they've always come back. Granted, I'm in FL, but I've had nights in the high 20s. And, down here, they're covered in leaves almost all year (maybe not Jan / Feb). You could try it indoors, though. Once you have a plant, it is extremely easy to propagate. I've probably got ~50 now, and I could easily have 500.