There are programs to play OGG vorbis, WMA audio, MP3, and MOD files.
For Divx and XVID (really cool version of divx) you need to buy (or wait for it to be free) GPCinema.
Google VirtualDubMOD, its a program that lets you convert any video to another, including WMV. Its not to bad, look at the tutorials on www.gp32x.de, and everywhere else too.
Either download and use Divx 4.12 or go to entware and get the XVID GP32 build and encode your videos to this, its smaller and slightly better quality for me. You must make your audio into MP3 format.
You could also use their MovieLink (?) program, just drop a file on it and it does all the settings for you, you still need divx 4.12 or xvid GP32 though. Its available at entware.com also
mth411
Edit: Sorry, must have typed this while you were posting above. Still valid info though.