Since I got my Droid Incredible phone, I've taken quite a liking to DoubleTwist, which incidentally will hook into your iTunes Library if it already exists. I'm not sure if it's an exact fit for your needs, but it's a little less proprietary and has some nice options for interfacing with non-Apple devices.
I'd also like to second Doug B's recommendation of Mozilla's Songbird, which is a stunningly well-made media management package. I haven't quite made the leap from iTunes YET, but it looks like all of the pieces are there for a good user experience.
YMMV, of course, but there are some options out there. I'm not terribly familiar with MediaMonkey, so I hope I'm not completely off-base.