I've been using friendfeed for just over a day now, and I'm already liking it a lot. The primary purpose is to aggregate the things you do on the web into a single place. It has build-in support for 41 different web applications, including flickr, youtube, digg, delicious, and twitter. Since it's all based on publicly available feeds, you do not have to trust them with usernames and passwords. You just tell friendfeed which services you use, and your username on each service, and you get one up-to-date page tracking what you do on each of the configured sites. In addition to the built-in services, you can provide it with custom feeds from anywhere on the web. Combine that with yahoo pipes, and there's probably not a thing you could do on the web that you couldn't feed into your friendfeed page.