VideoSpec - VideoSpec is a free AppleScript studio App (Xcode 3.
GSpot - GSpot is a Windows-based freeware designed to identify codecs used in video files.
Avicodec - AVIcodec is a free multimedia file analyser for Windows.
MediaInfoXP - GUI for MediaInfo, an open source tool for displaying technical information about media files.
CodecInstaller - Ever had a movie where you could only hear the sound and there were no video?
Media Tab - Media Tab is a nifty software solution that is extensively designed to display a wide range of details related to your audio or video files with only a single click.