3D formats based around surfaces such as triangles and other polygons. The format categories are listed on the software formats page.
DAE (COLLADA) - http://collada.org
Interchange format for 3D applications managed by the Khronos Group.
Format owned by Autodesk that is used for interoperability between digital content creation applications.
mdl (quake) - http://tfc.duke.free.fr/coding/mdl-specs-en.html
MD2 (quake2) - http://tfc.duke.free.fr/coding/md2-specs-en.html
MD3 (quake3) - http://www.icculus.org/~phaethon/q3a/formats/md3format.html
MD4 (quake3) - http://www.icculus.org/~phaethon/q3a/formats/md4format.html
MD5 (doom3) - http://tfc.duke.free.fr/coding/md5-specs-en.html
3DS - 3D-Studio File Format
ASE - 3D Studio Max Ascii Export Format
Lightwave 3D Object File Format
Wavefront .obj is text format for simple 3D geometry. It can contain vertex, UV position, vertex normals and faces made from these. Faces can be assigned to named objects and groups. As most OBJ writers/readers only support absolute indices it is not possible to merge two OBJ files by copying one into another. For that tools need to be used that rewrite the absolute indices.