Some of the developers of Firefox and the desktop app of the same name are currently working on a version of Songbird for the Android Market. This one is sure to be a hit with its customizations and plug-ins once they get everything going. At this time it already has 7digital music store and Last.FM support, but its sure to have more and will be a contender once everything is flushed out.
The app is still VERY beta (no playlists yet) but you can get in early and help them shape it by downloading the beta (you need to have non-market applications enabled) here.