Check out the tutorials for Audacity on removing vocals. It's not just eq. It works for bass in many tunes also. Let's you keep drums if they are panned at all.
There are plugins and tools that can do it based on harmonics. They can detect the fundamental and harmonics and zero in on what to remove. http://www.elevayta.com/product13.htm
There are much more expensive tools that work really well. Check out youtube demos
I'm sure there's more. Many songs are being decomposed, parts taken out, isolated, etc. Some really interesting stuff.