melatonin, and haul your ass to bed actually instead of doing stuff around the house. You will fall asleep, even if it's just because of boredom.
My sleeping cycle is deeply ****ed up atm, as I tend to not go to bed earlier than 4-5 AM. Then I end up waking up at 1 or 2 PM, sometimes even 4 PM. This really burns a lot of things I should do since I can't go to the bank or uni since they're only open in the earlier hours. Usually to get rid of it I don't go to bed one night and stay up until the evening -- the body needs at least 12-14 hours to make up for the missed sleep, but it gives me a better chance of going to bed in the next evening at a proper hour.
This particular cycle is a bit special: I began by walking up around 3:30 PM on tuesday, worked until 2-3 AM and then went to bed but got out of it after half an hour, took a shower and went back to work - I had a lot of stuff to do and some must-be-done errands downtown that I had to take care of, then in the evening I went to pick my brother from an airport 80 miles away and just got back. I'll be going to sleep but since I need to wake up before 10 AM I'm having 4 alarm clocks set up and my pal will be coming to wake me up if I don't pick up the phone at 10 AM.