I'm looking for some type of webservice where I can add a bunch of RSS feeds, filter them by multiple keywords, and subscribe to the results as a new feed.

For example:
* Throw a bunch of news site feeds together (Digg / SlashDot)
* Enter the keywords I'm interested in ("Messenger", "Patate Spears", "Blah")
* The resulting feed will only return items containing any of the keywords and can be subscribed to with any feed reader.

Preferably with flexible options:
* Don't show an item multiple times when they match multiple keywords
* Configure per keyword/feed if matches should occur in title only or if a match in description is ok too.

Pretty sure services like this exist, but don't know where to look. I don't want to install any software/script.

http://readwriteweb.com/archives/6_ways_to_filter_your_rss_feeds.php

It looks like Yahoo! Pipes can do what you want, based on this tutorial.

Thanks, Pipes does the job... very well too .