Remember those old cassette mixtapes you used to pass around with your friends? Blog Remix is a new application from Yahoo!'s Media Innovation Group that lets you mix together blog posts and MP3's from your favorite music blogs and then share them. Part of the challenge in creating this application, according to developer William White, was dealing with the differences in how music blogs syndicate their content. Some music blogs don't expose their MP3's in a consistent fashion -- some don't even provide RSS or ATOM feeds. He suggests a five level classification system to rate a music blog according to how well it shares its music and posts. For music blogs on the cutting edge, he suggests developers use the new hAudio microformat. Read more details in his blog post.