I saw this list of 120 RSS resources recently in the lifehacker… and it has the following categories…
RSS readers - Windows
RSS readers - OS X
RSS readers - Linux
RSS Readers - cross-platform
RSS readers - web based
Mobile RSS Readers
RSS to email converters
RSS Feed Validators
RSS-related plugins - Firefox
RSS-related plugins - Wordpress
RSS-related plugins - other
RSS Ping Tools
Feed directories
RSS tips [...]