smokin bud can make you sleepy, but when you wake up you'll probably feel pretty groggy, not so great for when you have to get up and go to work.
if your circadian rhythm is off, it means you're body wants to sleep at an unusual time... if your having trouble getting sleep altogether, it could be a sleeping disorder. I second rogue's suggestion of a foam mattress top. I just got a true sleeper (
www.truesleeper.com, visco-elastic foam developed by NASA, same stuff in the expensive tempur-pedic mattresses) The thing is truly amazing! It's so comfortable I can fall asleep just about anytime. $200 for a queen size 2" thick pad and my futon turned into a cloud.
or have some sex.. that should put you out pretty quick