Movie Masher
Browser-based online video editor and encoding API
Version 3.x available here on SourceForge has been superseded by version 4.x available on Github. The later is a port to JavaScript, PHP and Ruby - all dependencies on Flash have been removed, as well as some of the functionality it provided.
Version 3.x
---------------
Extensible Flash and PHP online video editor with effects, transitions, titling, timeshifting and compositing. Client side ActionScript provides a robust GUI that interacts with PHP through simple XML protocols for saving edit decision lists, handling uploads and asset searching.
XML is also used to describe the GUI itself as well as its underlying functionality - there is no need to recompile the Flash applets! But if you so desire then custom fonts, effects and widget classes can be written in AS3 - PixelBender support too, for effects and transitions.
http://www.moviemasher.com