3ds Models, .3ds was the original file format used by 3d Studio Max, however it is now often found in other programs.

ArchiDOM lots of free 3D Studio Objects, Textures, Materials. Tutorials

Es3dstudios undertake custom modeling jobs, and have a growing library of pre-made models.  They also have a free section with a couple of sample products.

Nasa These models are for anybody that uses a 3D software package. Most of the models are in the common .3ds format, which can be read by most 3D programs. Some models, however, are in their original .lwo, .fbx, or .obj formats to preserve details that would be lost in conversion.

Total Models Free models & meshes - 12 catagories with over 200 quality meshes in many formats

3D Lands A number of 3ds models, a few others too

3DM Lots of free models