Sheldon Brown has instructions for building a DIY fixed cup removal tool:

http://www.sheldonbrown.com/tooltips/bbcups.html

I built a tool to his specifications (about $5 in parts at the hardware store), and it allowed me to exert lots more force than an adjustable wrench or even a bench vise. That said, I still wasn't able to remove the cup and was forced to let my LBS do the job for me.