Spesoft video converter is a free, easy to use yet powerful single file and batch video converter handling many formats.
Easy: Convert 10,000's files in a few clicks with its simple wizard style interface or simply convert a single file.
Fast: Utilising the best and latest video libraries along with the .net framework.
Stable: Handles corrupt and invalid files with ease, keeping track of failed files and notifying you only when the process is complete.
Powerful: Convert between a wide variety of formats, with options to change transformation and filter settings along with the usual video quality settings.
Audio: Extract and convert audio from video files. Also convert audio files.
Web: Download or download and convert videos from popular video sites such as YouTube. Simply download or convert to other formats or audio files.

Supported file formats:

mp3, m4a, 3gp/3gpp/3gp2/3g2, avi, mpg/mpeg, mp4, asf, wmv, dvr-ms, mov, div/divx, rmvb/rm/rv/ram, flv/f4v/f4p, avs, m4v, mkv, vob/vro, m2ts, m2v, gif, mod, qt, ts/m2ts/m2t/mts, dpg, cdg, ogg/ogm/ogv, amv/mtv, dat

Plus many more.