Hi guys,
Well, I looked into the Plugin API and the WordPress RSS script source, and I’m afraid that a simple plugin to insert the iTunes RSS elements isn’t possible. Or at least, if it is possible then I don’t know how to do it. The problem is that the WP RSS 2.0 script outputs all of its RSS tags directly to the browser, without running them through a filter first. Only the post content, etc. are filtered, and the iTunes elements need to be on a higher level than that.
The only straightforward approach, therefore, is to replace the wp-rss2.php file with one including the iTunes tags. I.e., to hack the WordPress code. I’ll be working in that later tonight, and I’ll be happy to post what I have. Or if you’re impatient, Kevin Devin on the Yahoo! Podcasters group has already done the same thing. You can search the messages there for his code.
Or you can wait until Feedburner implements these elements, which ought to be any time now, since people are clamoring for them.
Anyway, sorry I couldn’t give you a simple plugin. I really wanted to.