I bought a Wacom Graphire tablet some months ago. It consists of a flat hard plastic tablet (think of it similar to a mouse pad) on which you can use a cordless mouse or a pen tool. A lead comes out from the top edge of the tablet and plugs into the USB port (Windows 98 only).
Although this model has less sensitivity than other Wacom tablet devices, it is excellent for editing images in Photoshop, the pen having 256 levels of sensitivity on the tip. This sensitivity can adjust either the amount of ink laid down when you draw, or the diameter of the tool brush (set in the tool options in Photoshop). The opposite end is an erase tip, also with 256 levels of sensitivity and is excellent for partial erasure of a layer (increasing transparency) so you can control how much of the underlying image is showing through the upper layer.
There is also a third middle button/thumbwheel on the mouse and a two position switch on the side of the pen, all of which can be configured for use (ideal for right-handed people). The options for mouse and pen include settings for use each device, applied to all programs, or any single program such as Photoshop. The configurations are to detailed to describe fully here, but one is certainly worth a mention - pop-up menus. Any button on the mouse or pen can be used to activate a pop-up menu. In Photoshop this pop-up menu can be configured for any combinations of key-stroke (some pull-down menu items in Photoshop do not have this facility). This can be very useful to quickly get to a command buried down several layers of menus of to frequently used operations.
The only disadvantage with this is that entering a long list can be very tricky, as the commands cannot be saved and loaded, or even moved up and down in the list as suggested by the dialog panel. Come on Wacom get you act together. A very, very, useful feature would be the facility to import or export this list to a text editor.