needed to merge some ogg vorbis files into a single file, after searching a bit, I find out that ogmtools operates on audio ogg files using any codec and on video ogm files using any codecs

$ ogmcat file1.ogg file2.ogg file3.ogg -o merged.ogg

as for avi files, you can use avimerge from transcode

$ avimerge -i file1.avi file2.avi file3.avi -o merged.avi

mpegs are even nicer, you can simply concatenate them together

$ cat file1.mpg file2.mpg file3.mpg > merged.mpg

If you would like to merge video with audio together into the wonderful matroska format you can use MKVToolnix. You can also add several audio tracks to a single video file.

$ mkvmerge -o MyMovie-with-sound.mkv -A MyMovie.avi MyMovie.ogg

Transcode, ogmtools and mkvtoolnix are available as mandrake packages, transcode is in Mandrake PLF Repository and ogmtools and mkvtoolnix in Mandrake Contrib Repository