Yahoo! Music have released a new (alpha) AIR-based tool: Blog Remix. Somewhere between Songbird, Hype Machine and Webjay, it lets you browse around music blogs, play tracks while reading the associated posts, and add the currently playing track to a playlist ('remix'), which can then be shared in various forms including XSPF (which carries the blog post HTML inside it) and podcast/feed.
It's still has a few bugs/interface awkwardnesses and doesn't seem to detect artist names, but looks promising. Would be good to have the 'share this playlist as XSPF' feature in Songbird, and perhaps a fuller packaging format for playlists: hypem.com/list + Songbird + Playlist Export Tool = Blog Remix, essentially.
Here's an example XSPF playlist exported from Blog Remix, with just a couple of tracks, but I can't find a way to open playlists in the app. I wonder if there'll be a central site to collect these playlists?