Yahoo launched their Pipes application a few days ago. Traffic seems to have almost overwhelmed the site, but if you can get on to it you will find a very nice, and well featured visual tool for combining, manipulating and presenting different data sources.
This effectively allows you to build your own data mashup in a matter of minutes. Yahoo provides a range of data sources already but you can add your own RSS feeds, for example, or scrape data from web pages and then combine them with image searches, maps, and internet searches. As Stutzman has pointed out, Yahoo has realised the importance and potential of RSS and Pipes should reinforce this in the minds of other developers.
I built a quick Flickr results display based on an Opensearch feed from our collection search in 30 minutes by pulling apart and looking at the way in which others had built Pipes to display Flickr results from other RSS feed data such as the New York Times headlines. The Opensearch feed is not clean enough to get a ‘good’ Flickr result, but with a bit more time Pipes could clean up and improve the results.