I have a plugin for Winamp that attempts to remove vocals. Since vocals are often equal from left to right, but other instruments are panned slightly to one side or the other, what it does is remove everything that is equal on the left and right channel. Depending on how the song was recorded it works anywhere from really well to not at all.
Is there anything that does the opposite, and removes everything except the vocals (so anything that isn't equal on both channels)?
What you can do in a DAW is split the left/right of the track then phase flip one side (removes vocals usually) then add them both to a bus and flip the phase on the bus.
add a new track of the raw song and you should just hear the vocals if the track is recorded right.