If you're a graphic designer, a graphics tablet is a must-have. Trying to draw semi-straight lines with a normal mouse is incredibly difficult, and uncomfortable. I used to just draw things on paper, and then I'd have to scan everything into the computer that I wanted to use. No more.
Wacom's ergonomic Intuos 3 graphics tablet is one of the best out there, especially for the price. $330 may seem high, but it has definitely paid for itself in my case. It comes with the tablet itself, with the surface you draw on, the pen (stylus) that has two buttons you can use for mouse clicks, and a 5-button mouse (one button is the mouse wheel). The tablet is surprisingly thin, but does extend about 3 inches more than the width and height of the drawing surface.
The best part about buying one of these is when you set it up for the first time, and write your name with the pen. It's so smooth and easy.
As for the dimensions of the one I bought (6"x8"), it's really a great size. You might think you'd need more drawing space than 6 inches, but you really don't. It would definitely be nice, but it would also take up more space on my desk than I would want it too. Plus, the USB cord is plenty long.