Welcome! I recommend the Wacom Bamboo Fun. For a little cheaper you could get a Bamboo Pen or Pen & Touch. Just make sure that you don't go for the model that's touch only. Those tablets have a little bit smaller drawing area.

If a new tablet is a bit out of your price range, you might check the auction and classifieds sites for an older Intuos or Graphire tablet. Just make sure you know what ports you can use before buying something, as some of them use a serial connection, and many computers don't have that port any more. As long as the cable is in good condition and a pen is included you shouldn't have any trouble with a used Wacom—they're very durable.

I couldn't recommend anything other than a Wacom at this point—some other brands are hit-and-miss on quality, and others just don't work at all.