Note: We don't normally encourage the discussion of tools in this forum, but for this topic we're making an exception.

The ReadWriteWeb has some interesting picks for the most important RSS and Syndication Technologies of 2009.

Top 10 RSS & Syndication Technologies of 2009 [readwriteweb.com]

• Facebook
  
• Twitter
  
• Echo, from JS-Kit
  
• Fever
  
• PubSubHubbub (and RSSCloud)
  
• Superfeedr
  
• Tweetdeck (and Seesmic)
  
• Postrank
  
• ActivityStreams
  
• The Breaking News Online iPhone App

Do you have any other tools that you would recommend for tracking feeds?

I'd add FeedDemon. Their switch this year from a NewsGator back end to Google Reader has improved syndication and allows for collaborative use of your feeds.