For those of you who want to try it but are a bit scared, the best way I found to teach yourself is to try riding with one finger of each hand on the handlebars. This provides you with the psychological comfort of still being 'attached', but also proves that actually your hands aren't really doing all that much. You can then gradually progress to letting go for longer and longer. I've tried this method on several of my more cautious cycling friends and they've all found it very successful.
My only trouble is that when I am being super cool and cycling with no hands (often to pull my jersey down as it always bloody rides up) my arse starts to slip forward on the saddle. Great when you've got an itchy arse, not so great for the washing basket.