I wandered across a couple sets of free utilities for dealing with .ogm (ogg media) files. There aren't too many tools available since this ogm stuff isn't really an official part of the Ogg project. I haven't used these since I don't deal with ogm files, but I have seen several questions posted in the forums related to the inability of many common programs to work with them.

http://www.bunkus.org/videotools/ogmtools/ - OGMtools for Linux. Command-line utilities to multiplex, demultiplex, merge, cut, and get information about the contents of OGM files.

http://cyrius.bunkus.org/ - Ogg Media File tools for Windows. Command-line utilities to multiplex, demultiplex, merge, cut, and get information about the contents of OGM files. The site also has a modified version of VirtualDub that should work with OGM.