Usually 1am before I consider going to bed, don't even feel tired at that point, plus I drink copious amounts of coffee in the evening, which is gonna keep me up.
have to get up at 6:30 weekdays for college..
weekends, varies, if I go down the pub/raving/etc then around 3am if at all, but if I'm gaming/msning etc, usually 2ish. Wake up at 9 so I can either go to work, recover from hangover and have a fry up. Or all 3.