Attached Link: http://interneteye3d.com/Tutorials/default.asp

You can make clothes in modeling programs such as 3D S. Max, LightWave, Rhino 3D; etc. I saw some tutorials at Internet Eye 3D Magazine. I think they were specifically for 3D S. Max, but you could learn from it and apply it to most any 3D modeling app. Once you've modeled the clothes, you can make the texture/trans maps, etc. with UVMapper and some paint program.