BarCampLondon3 in November 2007 is a quick practical run through by Cristiano Betta of how to use Yahoo! Pipes to build your "lifestream" - no, that's not "lifestream" in the sense of a cult religion, before you run away! (In fact Cristiano beat me to it in finding the video I'd uploaded before I'd had a chance to blog it).
Yahoo! Pipes lets non-programmers build mashups relatively easy, by drag & drop etc, of content from different web sources, as long as the source has a feed whether Atom, RSS or other XML (see my introduction to feeds - Pipes are obviously another great way of making use of feeds).
The official description of Pipes: "an interactive feed aggregator and manipulator. Using Pipes, you can create feeds that are more powerful, useful and relevant."
In this case, Cristiano grabbed feeds from blogs where he's a contributor, then filtered out the other posts to leave only his posts, then combined his posts with his feeds from other web services like Flickr, Delicious, Twitter and Upcoming - so he could display a single combo webpage with all his sources: his "lifestream".