3D objects files (.obj) are most likely one of the most common and widespread files for 3D modeling purposes and as such frequently used for 3D printing. It is thus no surprise that many 3D modeling or 3D conversion programs support the obj to stl conversion, which is actually the quintessential format for 3D printing.
Open OBJ file Open STL file3D viewer and converter with huge file type support
A website STL converter
A professional manufacturing data preparation software
A CAD 3D geometry translation software
A Mac version of the popular 3D visualisation software
A set of 3D modeling tools
A converter for 3D formats
An online CAD conversion service
A web-based freemium 3D computer graphics software
A 3D point cloud processing software
A CAD converter with huge format support
An open source multiplatform 3D CAD/MCAD/CAx/CAE/PLM modeler
A command line converter for 3D format
A 3D mesh converter
A free online 3D model conversion service
A commercial online CAD converter
A 3D CAD translation software
A dedicated CAD converter