I like the functionality of Yahoo Pipes, but don't want to leave the task of processing RSS feeds to a privately owned web service which might disappear tomorrow and I don't exactly trust my data with. I'd like to do this with software I can run locally (on a server or desktop; doesn't matter).
There must be something out there that handles some of the basic functionality of Pipes such as merging feeds, filtering, querying for keywords, etc. but I'm having a hard time finding it. There are various parsers that might do the job, but they're overly flexible and require much configuration upfront. Ideally I'd have something in the lines of a simple command that I can run in a cron job, or a daemon, which will fetch some feeds, perform the operations I want, and output or serve the resulting RSS feed. Any pointers appreciated.