My suggestion: Wacom Intous3 6x8. I picked up a brand new one from Amazon for about $200, came with some nice software, too. The overall size is about the same as my lappy, and about a half inch thick, so they fit in the same case :3 Well worth the price, as far as I am concerned.
http://www.monoprice.com/products/p.....1&format=2
The only minus is that the pen needs a AAA battery. For the price I can live with that!
The Wacom bamboo is nice, no battery but a smaller tablet at twice the price.
Wacon Intuos tablets are very nice but very expensive!
It is USB powered and the pen is wireless powered, so no need for batteries.