I've just 'stumbledupon' stumbleupon.

It's great! Install it now!

"StumbleUpon is a network of people and pages. It is a free tool which helps you browse, review and share webpages while meeting new people. StumbleUpon is backed by a community of members who explore and review sites they like. These reviews help everyone discover the best sites and meet like-minded people."

It's free and looks like it works for most major operating systems and browsers.

Check it out: http://www.stumbleupon.com/

Nomme

Yep, I'd second that. Been using it for a while. Great for when you're really bored. Firefox friendly too.