Yahoo Pipes is many things, but the one important to this article is its ability to allow you to create a mashup of RSS feeds with filters and restrictions. The beauty of Yahoo Pipes is that it was developed to allow the average business user to create rich applications without any programming experience. I have spent countless hours on Yahoo Pipes developing “pipes”. It truly is an amazing tool.
Yahoo! Pipes is a pretty old product, however, I still believe it's an interesting one and you can find dozen of implementation cases right away and from the top of your head.