Read. Do it right though. Sit down in a comfortable chair. Turn off your computer so you're not constantly getting up and checking your email. Maybe turn on some music. Allocate a sufficient block of time, so you can become truly engrossed in your book. Good fiction has a way of taking your mind elsewhere that no other medium can match. It's the most satisfying and fulfilling way to relax that I know of. edit: minor…
One of the downsides, for me, is that I can end up 'out of it' until I actually finish the story, yet other times, I'll stop reading at a lull in the story, and never pick the book back up again, because I didn't stop at a point that was engrossing enough to pull me back into the storyline (e.g. Diamond Age).