Filter My RSS is a very useful, simplistic service that allows you to create filtered feeds (from existing feeds) using keywords. I have used something of the same nature on various other services but this is a once stop shop and it is very easy to use. Also, considering the fact that the filtered feed URI can be hand crafted and the simplicity of the service, I am assuming that it can scale very well. This is a classic example of an itch scratch software that can be useful to others as well. Here is the WeblogToolsCollection.com default feed, filtered for the keyword WordPress.