I have a circadian dysrhythmia [link is a nifty PPT]. It began at the ALA thingy in Orlando and has become exacerbated by working the overnight shift earlier in the week.
This is really a pain in the neck because I have stuff to do during the day. I have found that I can nap for ~45 minutes about five times a day and function productively the remainder of the day. That worked fairly well in graduate school. Unfortunately I don't find many employers willing to let me take a 45-minute nap at noon and six. They really should because I would be remarkably useful during my waking hours.
If there were a union that negotiated naps and milk and cookies at work I would join.