good ta know. I'm maybe a half-step ahead (I do hats, maybe shoes, some armor pieces...sux, but I'm just startin'..;)  any good modeler will do (I use Wings 3d). The reason for hats, shoes, etc., is they don't have to bend.

Here's a sample way to do it- don't try to model the whole thing, try to model a basic part (say a head, chest, shoulder, etc). Export that to your modeler, then work on creating a piece of clothing to fit (it's harder than it looks..;). One thing Poser does is use a scale different from the rest of the world (Importing a part from Poser to a modeler will give you an eentsy, itty bitty, tiny little item).

Then, once you get the clothing item to fit on the body part, it needs to be textured (UVMapped..hoo boy, there's another 2-3 pages of text).  Then it could be exported into Poser (have to keep track of your textures, there's guidelines for where they get put as well...just remember not to begin your texture directory with a !..;) Then you can use it like other clothes

Ok, this is very confusing and complicated, but this is the basics of how clothes can be made.  I left out about 10 pages of details. Yes, it's complicated at first, and yes, it takes a lot of work. After about 2 years, I'm still doin' baby steps. But it is possible, and it is rewarding (get good enough, and it can be financially rewarding as well...well, some, anyways..;)

There's tutorials for every step of the way, so don't lose heart. Download some freebie modelers (say Wings 3d, Blender, Anim8tor, etc) and just fool around. If you feel like it's something you want to try, you can always upgrade to a more complicated or spendy program (Lightwave, Maya, Silo, Rhino, etc).  It can be done. Everyone gets to the point soon after getting Poser where they want to do their own clothes.

All of the above sites are good for tutorials. And someone better fire Doc's publicist..can't believe he doesn't show up..;)  I'm just trying to break it down to basic steps. But even doing that, everyone develops their own style, so feel free to give this a raspberry if'n it don't work for you..;)
Trekkiegrrrl (Ernyoka1) used to have a long list of Poser tutorials on her site, they might be there still..

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)