MeshLab is made for processing 3D scans. Point clouds can be trianglulated into triangle meshes using various techniques. Models can be smoothed, cleaned and repaired.
MeshLab is also a great 3D model viewer and converter. It can convert between many 3D file formats:
import:PLY, STL, OFF, OBJ, 3DS, COLLADA, PTX, V3D, PTS, APTS, XYZ, GTS, TRI, ASC, X3D, X3DV, VRML, ALN
export:PLY, STL, OFF, OBJ, 3DS, COLLADA, VRML, DXF, GTS, U3D, IDTF, X3D
