For those who haven’t seen it yet, Ramen HDR is a free, open source node based compositing software.
Created by Esteban Tovagliari, it is currently available for Mac, Windows (64bit), and Linux. Ramen is a nice alternative to Shake, Fusion, or Nuke. It’s current capabilities are not quite where the commercial software packages are at, but I did use it for some decent greenscreen compositing work. For the freelancer or small shop looking for an inexpensive, easy to use solution, Ramen might work well for you.
Here is a tutorial I wrote: Greenscreen with Ramen
and the final result: Greenscreen Composite