I've had excellent success with melatonin (2-3 mg) in getting myself on a good sleep cycle. I take it about 1 hr before I want to be sleeping; works like a charm. Before I used to sit in bed for hours waiting to feel sleepy. Other people here report similar effects.

Only drawback is sometimes I feel groggy in the morning, and I've had lots of crazy dreams on the nights I've taken it (or maybe just remember them better?).