Blender

From MITVWiki

Blender has a very advanced node compositing system as well as a sequence editor. This makes it an excellent tool for color grading as well as compositing. The 3d capabilities can be used for everything from simple title sequences to custom transitions and advanced special effects. Although the interface takes some time to learn there are a number of blend files that are prepared with a single video editing task in mind and can easily be used without knowing how the 3d system works. http://gvfx.blogspot.com for transitions, http://indiworks.wordpress.com/2007/07/20/how-to-make-2d-titles-in-blender-2d-title-presest-v01/ for titles

Blender is also cross platform http://www.blender.org