you can also check out Ninja Topo.. Its a free script on creative crash http://www.creativecrash.com/maya/downloads/scripts-plugins/modeling/c/ninja-topo http://www.youtube.com/watch?feature=player_embedded&v=drQsYROMgrU
ohh boy... so many apps in which you can retopo these days... from max with its surface snapping ribbon tools and to its free scripts for it and payed scripts like Wrapit(looks really good check it out) to topogun or 3dcoat or even to blender with those looptools and bsurface(free addon for blender) to other software that…