FeedShake looks like a very useful service for merging, sorting and filtering multiple RSS feeds. You give it a set of feeds and it produces a URL for a new RSS 2.0 feed. You can optionaly filter the feed items, selecting only those which have or don’t have certain words. Once interesting design decision is that they don’t really parse the input feeds, but rather just look for <item>…</item> blocks in them. I don’t know if this is a good idea or not. I guess the onus is on the users to start with reasonable input feeds.

Related posts:

1. Google opens AdSense for feeds
2. Finding Feeds That Matter on the Blogogsphere
3. Preferential Attachment in Feeds
4. Feedburner to include AdSense ads starting next week
5. Storms on Planet Social Media Research