Rui Carmo has integrated Bayesian filtering with RSS aggregation to improve his feed reading. So far the results look pretty good. His setup involves receiving new RSS items as SMTP e-mail messages, (e-mail, good old e-mail) which supports highly tuned and customized user interfaces along with automated scripts to process the messages in the background. At the same time it sounds like it was pretty easy to whip out a web interface to label messages if needed.
Any web or desktop aggregator with sophisticated APIs and a dirt cheap labeling mechanism (probably tagging) could replicate this to good effect. Then again I can't really think of any such combinations.
But I would be glad to be enlightened.