We accept AVI, MPEG, QuickTime, Real, and Windows Media, 100 MB maximum.
mencoder -idx input.ogv -ovc lavc -oac mp3lame -o output.avi
Where "input.ogv" is the file you wish to convert, and "output.avi" is the file that you wish to convert it to. The original file is not changed or deleted in this process.
Looking at both files, it appears that Vimeo is better at the conversion process than I am ;)