Is it a cartridge BB or a cup and cone? If the latter, you can try Sheldon Brown's DIY BB cup removal tool:
http://sheldonbrown.com/tooltips/bbcups.html

Works like a charm for me. Be sure to soak the cup with penetrating oil, and as stated above, unscrew it in the correct direction. Clockwise for most applications, counterclockwise for Italian and French. Also, if you use the DIY tool, you'll need a low profile deep socket for the inside of the BB shell. Tighten the bolt like hell, making sure the bolt head is on the outside for English thread (clockwise to loosen) or the inside for Italian or French (counter-clockwise to loosen).