I use Empathy. I also use mpd. Now, the players I used earlier, they'd have a convenient plugin that sent "Now playing" to Empathy. I hadn't found one for mpd yet, so in true FOSS spirit, I jumped into it and decided to write my own. I'm not particularly a fan of sending my "Now Playing" to the world, but I just like to know that it can be done, even if I'm on mpd.
One can checkout the 0.0.2 release from gitorious using the following command. To compile it, one needs libmpd-devel and telepathy-glib-devel. Building it is as simple as ../configure && make.
git clone git://gitorious.org/mpde/mpde.git
I'd like to warn you, that this is a "just works" release. I need to work a lot more on this. Please have a look at the TODO file for information. Please send any bugs/feature requests to the emails listed in the AUTHORS file.