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. Ming and I were recently talking about how personalization is the key next theme for the web. Here's an example of a "community" browser, you wander around the Internet and sites that you like, you say thumbs up and others can wander and look at it too.
Kind of like Tivo for the web.