This was suggested just over a year ago, but wasn't really addressed.
Is it possible to include a DAAP server as part of the subsonic package? As Subsonic already indexes the media library, it seems it would be just a little bit more work to include a daap server. Firefly Media Server (used to be mt-daapd) is an open-source project for a daap server.
hxxp://www.fireflymediaserver.org/
A daap server would be an awesome addition, as it would allow any media player with daap support (such as iTunes and Rhythmbox) to browse the entire music library without using the web interface... I won't lecture you on the basics, I'm sure you know what it is.