Feedage is a free fully categorized and searchable RSS directory, that also lets you blend two or more RSS feeds together, receive your favorite RSS Feeds by e-mail, enable custom filters that will only notify you if the RSS Feed has been updated and more. They also offer a HTML

Validate and fix your feed at FeedValidator. Works for Atom, RSS and KML.   Related posts: Create Custom RSS Mashups Email Your Feed Info On Your Feed, Cache, Search And Links

Email your website’s feed and automatically build a subscriber list with Google’s Feedburner.   Related posts: Compare Number Of Feedburner Subscribers Validate And Fix Your Feed Feed Your Blog To Twitter, identi.ca, HelloTxt or Ping.fm

Combine feeds from several sources at FeedInformer and publish them as one feed on your website.   Related posts: Create Custom RSS Mashups Email Your Feed Test How Well (or Not) Your Colors Combine

Find your competitors’ most popular posts based on the number of comments, diggs, delicious bookmarks and more at aiderss.   Related posts: Compare Social Media Performance Social Media Search Find Top URLs Shared On Twitter