Veejay is a visual instrument and real-time video sampler. It allows you to "play" the video like you would play a piano. While playing, you can record the resulting video directly to disk (video sampling).
QuickTimeTcl is an extension package to Tcl/Tk that runs on Mac OS Classic, Mac OS X, and Windows. It provides a high level interface to QuickTime from Tcl for both application development and scripting from console.
iVideo is a multitrack video editing software on Mac OS X, created in Cocoa (Objective-C) and using QuickTime with a cool look & feel ;-).
It can import and export all formats supported by QuickTime (including mp4) and can use digital cameras too.