Found - Normal map generator for OSX
polycounter lvl 18
I stumbled upon this today - a standalone normal map generator for the mac. Works a treat, it's very similar to the Nvidia filter, though it's obviously not embedded into Photoshop, so you lose the nice layering ability tht nvidia gives you.
http://episteme.arstechnica.com/eve/forums/a/tpc/f/8300945231/m/726000575831/p/2
http://episteme.arstechnica.com/eve/forums/a/tpc/f/8300945231/m/726000575831/p/2