Walk2Web is an incredibly addictive (though not time efficient) web-based surfing tool that allows you visually browse the internet using links that connect one website to the next. As if that wasn't engaging enough, it is also possible to create a user account that can contribute to the rating, tagging, and commenting on any site you happen upon. There are also icons to send pages to digg, StumbleUpon, del.icio.us, and Hatena.
*Note that there is a text reader that is enabled by default on the system that will read page titles aloud when you click on a link. If your speakers are cranked it is quite a surprise.