Shake

From Redhax

Shake is a motion-picture and video compositing tool now sold by Apple.

Its node-based compositing features (like competitors Nuke or Fusion) and affordable (~$500US) price tag makes it the tool of choice for many indie filmmakers. Primarily, it's used for bluescreen/greenscreen and special effects work. It's also resolution-independent, so it can manage RED's native 4k size (though not in real time.)

[edit] Shake and RED

As of April 2008, there is not a way to directly import .R3D files into Shake. However, Shake was originally designed for a DPX/Cineon workflow and thus can be used quite effectively with RED footage converted with REDCine or REDAlert!.