My favorite is this http://www.neubauladen.com/product/1231 and you can buy entire colleciton of humans and objects at less than $60 http://www.neubauladen.com/catalogue/NB-Digital/2/Neubau%20W...
(I have no affiliation to these guys :)
Hers an example of using an avatar with some purchased poses (layout and image effects were added with comic life): http://larrymade.com/samples/tech-noir.png
Warning- SL is kinda fun, you might get lost in it for a while before seeing productivity.
You could have a sort of "click and drag" interface to reposition the limbs arbitrarily, and possibly either another mode, or a set of input boxes, allowing you to change properties of the limbs (e.g. muscle width, muscle length, limb length).
I too would be interested if anyone knows of such a thing.
If you only need very basic stick men style images, use Pivot Stickfigure animator.