If you do most of your work sitting at a computer and have a window nearby, open it up when the weather is nice.
Not only will the fresh air be nice, but you can turn off your air conditioner (if you are at home) and save some power as well. If you are at home, turn on your overhead fan or use a small floor fan to keep a nice breeze going.
This really can be a boost when you are looking at a computer most of the day. It is for me at least.

Jason Faulkner is the man who brings you our daily tips. He is based in Atlanta, Georgia.
There you see it: Proof that Windows is always useful when computing – from a Mac user.
…Before anyone says anything: I had it in my head that it was David Risley who wrote this article, and only realised I was wrong after I posted.