Mashable.com has created an ‘Ultimate RSS Toolbox‘ with over 120 resources. Check out

RSS Readers - Windows

RSS Readers - OSX

RSS Readers - Linux

RSS Readers - Cross Platform

RSS Readers - Web Based

Mobile RSS Readers

RSS to Email Converters

RSS Feed Validators

RSS Plugins - Firefox

RSS Plugins - Wordpress

RSS Plugins - Misc

RSS Managers

RSS Mixers

RSS Ping Tools

Feed Directories

RSS Tips

RSS Tools - Misc

Phew! Yeah, and they came up with more than just the headers. A lot of work. A great resource!