http://followcost.com/
Enter a twitter username and get a "follow cost" for them. How many tweets they post and how many are replies, as well as, golden, how many tweets are exactly 140 chars!
http://plagger.org/trac
Plagger is like pipes for news feeds. You can read feeds from almost anywhere and output them to almost anywhere. It's written in perl.
http://www.xfruits.com/
xFruits is a sort of Yahoo! Pipes type service where you can take content and munge it into different forms. RSS to Atom, RSS to email, x RSS to 1 RSS, etc, etc.
http://www.dapper.net/
I think Dapper turns any static site into dynamic content (RSS, XML, and more), widgets, facebook apps, etc. It's a content dynamifier I suppose.