MediaCell Mobile Video Converter
You can find some pretty sharp one-off freeware tools that convert media files to a single platform, such as Videora iPod Video Converter or PSP Video 9,but the Mobile Video Converter is more like a Swiss Army knife with several dozen tools. It's capable of converting a wide range of video file formats to either the 3gp or mp4 file formats supported by more than 100 mobile devices.
The program permits advanced users to modify the video quality settings, such as framerate or the encoding bitrate, but doesn't require novice users to make complicated decisions about these obscure parameters. You don't even need to know the intricacies of how to move the files to your mobile device: MediaCell provides clear, concise directions about what you do with the files after you've converted them.
The free trial version doesn't cripple the product's features; its only limitation is time. After that, you have to pay to continue using the program, but you get lifetime free upgrades and email support.