Converting .avi, .divx, .wma files, etc., can be fairly annoying or costly, depending on which program you download. I just recently found a program called 'VisualHub' VisualHub: The Universal Video Converter for Mac. which has an unusually easy user interface. It will convert most video formats to most other video formats, even optimizing viewing for every type of IPod. It is 23 dollars to purchase, but you could easily find a registration code on a BitTorrent.
Thought I would share.