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.
Thanks. I subscribe to many feeds and I often find myself wading through lots of things I am not really interested in. I will be making use of this service.
The filtermyrss site seems to be a bit slow. So it’s worth noting that you can use Yahoo Pipes to do the same basic thing, as well as a whole lot more. The interface isn’t as simple, but it works quite well.
Seconding Otto’s recommendation for Yahoo Pipes – The functionality scales very well as you try and add more complex filters to a feed.