Yahoo! Pipes

Pipes is an advanced tool for manipulating web data. A simple example would be fetching an RSS feed and returning the articles about a certain subject or written by a particular author. But Pipes can do much more. You can create a pipe that searches for pizza places in a zip code, automatically excludes the Dominos, and displays pictures of nearby parks (where you can eat the pizza) from Flickr.

There is an excellent little demo of Pipes at MurphyMac's - after watching that - go ahead and take Pipes for a spin or check out what other users are doing.