OmniWeb is my browser of choice, but I've always been envious of Internet Explorer 5's ability to navigate links via the keyboard. Today I stumbled across a similar feature in OmniWeb 4.1sp36 (sneakypeek 36)! It may be in earlier versions as well - I don't know.
Press command-downarrow to move forward through links on a page (the currently selected link is outlined with a box) and command-uparrow to go the other way. Press the return key to "click" the link.
If you don't have it, you can get the latest beta ("sneakypeek") build of OmniWeb 4.1 from Omni's server.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2002020323150885