To call my sleep schedule at the moment a "schedule" is, well. So because it entertains me to do so, because it's mildly useful to my friends to be able to check when I've been sleeping as a loose predictor of when I'll be up, and because it will probably be of interest to a doctor assuming I ever wind up seeing one, I have been trying to track when I sleep.
I use Google Calendar. I have created a separate calendar strictly for my sleep schedule. It can be public, private, or shared with people. Mine is public. I have set up a tinyurl pointing to it (sadly to an un-useful view): http://tinyurl.com/azz-sleeps-when
Using Google Calendar to track is useful enough, given that I am often near a computer. Sometimes I don't remember (notice that there are sometimes blank days, and I am not often given to a full 24+ hours awake) and sometimes I backfill.
I now have a smartphone. Yay smartphone. The phone is smart enough that it can interact with multiple Google calendars at once. It is easy enough to work that I can manage it when I am out of my mind with sleep-grogginess.
The phone has a charger cable near enough to my bed that I can go to bed with the phone on the bed with me. I have been maintaining scrupulous enough "sleep hygiene" that I can usually be asleep withing twenty minutes of climbing into bed, and I have been getting practice at knowing my level of drowsiness enough to be able to tell how long it will take me to be out. When I get into bed, I take note of the current time, and open a new event on my sleep calendar. (The first thing I do is turn off any reminders for it, because the buzz and ding are not the sort of thing that are conducive to sleep.) I have it start at the time I think I will fall asleep. If I remain awake for a while, I check the clock, and adjust the start time of the sleep event.
When I wake up, I check what time it is. I tend to still have the calendar event for sleep open, unless the FUCKING PHONE has gone APESHIT in the night and run out of memory and rebooted. (Argh Palm Pixi.) I adjust the sleep event to have the correct end time.
I track naps on this too, not just full "nights" of sleep.
My phone takes care of automatically synchronizing the local copy of the calendar to Google, and Bob's yer uncle.