FeedBurner

I've been using Feedburner for a while to convert the ATOM feed that Blogger supports (don't get me started...) with the RSS feed that people actually want. There's a lot more to it though - you can have FeedBurner collect usage stats and it provides a form of bandwidth insurance for your feeds. Say a bazillion people subscribe to your feed and are requesting it once an hour - it will be a little expensive. If you use FeedBurner then they will get stuck with the bill! Also FeedBurner can provide gzip support and handle IF-MODIFIED-SINCE/ETAG support to make aggregators more efficient.