Most of the links I got with that search were how to watch .ogm on a Mac which I've already got. It doesn't seem like there's a program out there to actually convert them to .avi's though. The best thing I could find is this post from another forums:
"this is a multistep process, but it gives me great results with OGM files encoded with Xvid video + ogg audio.
-I use ogmtools to demux.(this gives me an avi and an ogg file)
-itunes to convert the ogg files to comparable mp3 files.(I have the Xiph quicktime codec installed)
-ffmpegX to mux the mp3 and the avi(from the demux)
this gives me an avi file which plays great in quicktime.
to burn to DVD, i use VisualHub."
I suppose I needa figure out how to work all those programs now, ogmtools looks the worst, looks like you have to use Terminal.