I have a Wacom Intuos 3, and I love it. And I'd highly recommend the brand (wacom) because it's a good quality, and the pen doesn't need batteries or a cord or anything like that.
As for which model, it depends how much you're willing to pay and what you plan to use it for. The lower cost ones have lower levels of pressure sensitivity. Having not used one, I can't say for sure. But, 512 levels of pressure sensitivity stills sounds pretty good.