I've been successful with bok choy, red cabbage, swiss chard and beets. Really want to try spinach and lettuce.
Also visit: http://citygirlfarming.com/Gardening/GrowingFoodFromKitchenScraps.html
How to Grow Celery from Stalks
Did you know that you can regrow celery from the leftover stalk stub? It's true. Just take a freshly cut bottom (the whole stub), soak it in warm water overnight, then plant it (cut side up) in fertile soil. Water well for the first few days and within 1-2 weeks, you should have a few slim but steady stalks. Why fuss with seeds if you don't have to?