I'm looking at creating basic textures and transparency maps for some of the poser clothing, and while I know how to make UV maps, I find it difficult to create the map in 2d. I was wondering; is there any programs that will allow me to to load the clothing object and "paint" directly upon it in 3d, then output the results to a texture map?  I'm willing to give up some precision in my results if it's necessary.

Yep.. C4d, 3d coat and zbrush. Least you'll spend is $100.. the most is $800 or so I think.

Cinema 4D/Bodypaint is probably the most comprehensive and powerful modeling/UVmapping/texturing suite you can get your hands on for any price - it's the most expensive option named but it's also the most flexible and powerful and will probably give you the fewest headaches learning it.  Don't expect that you can do absolutely everything in 3D paint mode, you'll very likely have to do quite a bit of image manipulation in 2D tools also, whatever application you pick.

Carrara 7 Pro also now has 3D painting capability.

Argile is a low-end option, but I've never really tried its 3D painting capabilities, mostly just use it for sculpting.

I'll second 3dc... Bodypaint is good of course, but it's overkill for most texturing. In my experience, a 3d painter is mainly useful for stuff like fixing seams and in cases where the UV map is a mess. Can also work nicely for creating wholly original textures by hand. All this you can do in 3dc without spending a bundle on bodypaint.

For everything else, nothing beats photoshop. It can handle far heavier files (and texture files can easily get to 700-800 MB) has all kinds of neat editing tools that you wont find in any 3d painter and is very fast to work with. It should be your main workhorse.

Thay all have demos

so ya can try them out

Do not have 3D Coat or Modo but thay look fun.

I have C4D,BP & zBrush there a lot of fun.

Photoshop CS4 Extended also has 3d texture painting capabilities.

I've heard good things about Stitch Witch from DAZ, and it's under $50.00. 

http://www.daz3d.com/i/3d-models/0/stitch-witch-1?item=8201&cat=&_m=d