+1 for marvelous, Very powerful peice of software. Easily the quickest way to iterate on clothing for characters and you can easily move outfits from one character to another. The simulation quality is actually very good and produces much more believable and realistic results than sculpting by hand will. The more you use it and build a pattern library the quicker it becomes to outfit a character.
Also 3d-coat, it has a cloth simulator built into it as well, Basically you model the clothes using the retop room, then simulate and sculpt the cloth. Not as good as marvelous designer but better than Zbrush.