Chad put up this really interesting article about Yahoo! Pipes. So, here’s the deal with pipes, away from all the hype and buzzwords. If you’ve got something (a web page, a spreadsheet, Flickr photos, OPML, …) that can be accessed from the Internet-at-large, you can use Pipes to fetch it, manipulate it (i.e. filter items, recode items, etc.) and put it into an RSS feed that you can then retrieve with your RSS reader. That’s what they mean by “aggregate, manipulate, and mashup content from around the web”. It’s not difficult to do if you have ANY programming experience at all — it’s a visual, drag-n-drop environment with a lot of help.
Give it a try and if you can’t think of something you can use it for … well, you’re not trying hard enough 🙂