Attached Link: http://hof.povray.org/

I only have experience with Pov-ray and (only recently with the free download) Bryce.

Poseray will convert Poser objects and lights (except Poser 6's IBL's though you can get the same effect with radiosity).  The image based textures convert with no problem, but the procedural nodes won't.  Pov-ray has it's own procedurals that will do everything Poser's will and more, but they take a little getting used to (there's no graphical interface, only text files).  They can give some amazing results once you get used to them though - I've used Pov-ray procedural textures to put lettering on car tires when I was too lazy to uv-map it.  I think the image and source is still somewhere on my old computer - I can dig it out later if anybody is interested.