I'll go with Tunesy and recommend Wings3D and Silo (& its topology brush). Silo has good forum support, but is very focused on Silo2 at the moment. Here are a couple of silo specific threads for creating clothing:
http://www.silo3d.com/forum/showthread.php?t=4491
http://www.silo3d.com/forum/showthread.php?t=5614

Hexagon is probably pretty good for this sort of thing, but I don't use it - have a look over at daz3d.com and polyloop.net for Hex2 tutorials. Here's a step by step tutorial for Hexagon:
http://www.tigerdesigns-online.com/extras/Dress%20Tutorial.pdf

I don't know what stuff you've got for poser, but someone has already mentioned PhilC so I'll suggest the Poser Tool Box Shrink To Fit as a possible starting point for creating clothing.