Straight from the Google Labs: How to navigate Google without a mouse.
“Google Keyboard Shortcuts allows you to explore search results quickly and easily without taking your hands off of the keyboard to use the mouse.”
Be aware though:
Internet Explorer 5+, Netscape 6, or Mozilla
Cookies enabled (optional)
For Macintosh, Netscape 6 or Mozilla is recommended. Google Keyboard Shortcuts does not fully work on Mac Internet Explorer.