Free, and supports a SHIT ton of formats, except .b3d is not one of them. However, it includes a python plugin system.
I might get to eventually making the Python script for the B3D model format but if anyone wants to try their hand, please do.Noesis supports Python through a native binary module. In order to add format/functionality support, put .py scripts in this folder which implement a method named "registerNoesisTypes".