The .MOD file format is used by various digital camcorder models (I.E JVC Everio) to save their videos. These files are often accompanied by small .MOI files (See links below) which contain the videos' time-stamp information.
The .MOD format is simply a MPEG2 formatted video, and if you simply wish to view the files on your computer, it is reportedly safe to rename the extension from .mod to .mpg or .avi
The known camcorder models that use the .MOD format are:
JVC: GZ-MG30, GZ-MG70, GZ-MG37, GZ-MG77, GZ-MG505, GZ-MG130, GZ-MG155, GZ-MG255, GZ-MG555
Panasonic: SDR-S100, SDR-S150, SDR-S10, SDR-H18, SDR-H200, SDR-H40, SDR-H60, SDR-SW20
Canon: FS100, FS10, FS11