I use VisualHub. http://www.techspansion.com/visualhub/
It can covert your file to many formats and sizes depending on your need. Just go to the site and see if it will work for you. Here just one quote "Fast conversion from nearly every video format to iPod, PSP, DV, DVD, Tivo, AVI, MP4, WMV, MPEG and Flash."
I use it frequently to convert many types to video files to MP4. It uses H.264 encoding and works very well. Then I will put those files into iTunes. Some conversions can be large and this can shrink a file to save space.