Stoyan Stefanov has an interesting way to "automatically" create podcasts based on your blog posts using PHP, ffmpeg and the "say" command in OS X to create the mp3 result.

ffmpeg is such an amazing tool, looks like it's for video what ImageMagick is for images. An all-powerful all-formats wicked cool command-line tool. This blog post is an introduction to some of the MP3 capabilities of ffmpeg. I'll use ffmpeg to transform a blog post into a podcast-ready mp3 file.

The post shows how to use PHP's DOM functions to grab the title and contents of your post (a simple example, at least) and push that information out to a text file. From there, the "say" command is run on it with the "output" file parameter and the result is sent to ffmpeg for compression into an mp3.