This is what I used to do or still do:
Coffee, coffee coffee
Sleep, sleep, sleep.
Play some computer games
Be more active in math forum than usual
Totally forget math and play some chess. I'm a professional chess player, and funnily my math block and my chess block are inversely proportional.. whenever I excel in math, my chess gets extremely poor and whenever I'm bad in math the chess suddenly improves.
Sports
TV
Read math instead of do math (and like the other poster said, do a lot of not-your-research-area readings as well).
In other words.. when I get my "block".. I procrastinate and try not to feel guilty. Because I know that this type of procrastinating is actually the good type of procrastinating :P
and if you want me to state the obvious
9. Socialize and tend to your lovelife. Some people can do magic