FeedBurner
Feedburner is best known for its Atom-to-RSS conversion: you give it an Atom feed URL (e.g. the one you have in a Blogger site), and you get a http://feeds.feedburner.com/(a_name_you_pick) URL that contains the up-to-date RSS version of it. FeedBurner actually can convert from and to any version of RSS or Atom.
FeedBurner also supports:
- statistics on feed or on post level
- adding related Amazon links to (some of) your feed items
- splicing Flickr photos or del.icio.us/Furl links in your feed
- insert a Creative Commons license in your feed
- SmartCast for converting Blogger linkblogs to podcast compatible RSS feeds (with enclosures)