DSS3 and xmarcelx have the right idea.
The "karaoke machine" DAW version:
Split the stereo .wav into two mono channels and flip the phase on one.
Since lead vocals are usually mixed right up the middle, you're cancelling it out -- along with everything else that's panned dead center (kick, snare).
This is pretty much going to sound tinny and shitty, but hey, the lead vocal is gone.
Sooo... Throw on a linear phase eq and make a pretty broad high end cut to ease the harshness. Then load in the original stereo .wav and high pass it around 100hz and blend to taste to get back some of the bottom end.
You'll be surprised at what's still there when you do this on a well mixed track. You can really learn a lot about panning, background vox, reverb and delays, etc. The kind of details that make a mix come alive.