I was messing around with Reeder recently and found that my blog did not parse correctly. This was surprising to me, since I already matched the RSS 2.0 Specification.
To try and figure out what was wrong, I started downloading other blogs that worked in Reeder. I found that they either embedded the entire html content into the description tag, or used the content:encoded tag. I had never heard of the encoded content field; it isn't in the RSS 2.0 spec...
Well, it turns out RSS uses namespaces for extending functionality. The content:encoded tag is a part of the popular Content Namespace Extension. So one quick addition later, and my blog now properly renders in feed readers!
Extras
While I was at it, I also spruced up the channel description by adding some more optional tags: webMaster, lastBuildDate, language, and docs.