program for compressing video

who knows a good ( free ) program for compressing video, like for avi and mpeg etc.

I would recommend VirtualDub ( http://www.virtualdub.org/ ).
Input can be raw, avi or mpeg-1, output is always avi. If you want to process mpeg-2 or add several audiotracks, then there are extensions available. Wmv, asf are not supported since M$ is a little funny about it.

Please note that this program might not be suitable for newbies.