Could a mouse get even more portable? It can and it does. Microsoft's Arc Touch Mouse folds flat when you're on the go and pops up into a more hand-friendly shape when you need to use it. A wireless USB receiver is plugged into the computer to communicate with the mouse (when you're on the go, it unplugs and can be magntically attached to the mouse's underside, so you never lose it) and the touch-sensitive scroll strip lets you whiz through web pages with minimal effort.
Price: $70 at Amazon