my favourite:
http://www.3drad.com/
this one is free, but they are still workin on it. i tried it once, but i wasn't so much into 3D at that time
http://www.3d-rpgbuilder.com/products.htm
then there is this 3D thing from eb!, but i don't think that its so good...and its PS2 only, i think. there is no downloadable version, i think.
the 3D gamestudio (shareware, i think)
http://www.3dgamestudio.com/
http://www.3impact.com/
there are many more (free!) editors, but i don't want to search now...
