Here is a very good list of free multimedia file converters software:
– Pazera various distinct products for audio and video conversion
– Freez it has extra features over conversion like screenshot capture and dvd ripping tool
– FormatFactory supports a lot of audio/video/image formats; support for mobile devices, includes 6 dvd rippers, it’s multilanguage and many more!
– SUPER a true “universal” converter
– Koyote Soft various software/utilities both for audio and video (DVD and Flash FLV format included)
– XMedia Recode it has hundreds conversion profiles “templates”
Clone2Go Free Video Converter and Clone2Go Free Audio Converter
Free Video Converter, easy to use, Office style interface
Free Studio, an installation for many programs, all in one audio and video converter
MediaCoder for Windows but it can run also on Linux and Mac, support various mobile devices and recent formats like WebM and VP8
Hamster free video converter convert in few clicks, support many devices (over 200), integrated video player
Handbrake multiplatform (Windows, Mac and Linux) opensource converter