I finally got the Rhythmbox integration for Drivel working. It's a hideous mess of bonobo, autotools and scary magic. What I love the most is that it's mostly boiler plate and error protection with about 4 lines of actual code.

drivel :: getting the current song from Rhythmbox
I haven't committed it yet, as I haven't tested it on a machine without Rhythmbox, but if people are interested the patch is here.

Drivel will soon be able to support other blog APIs. Stay tuned.