I have been working with a company in London called Onsight to develop a plugin for FCP to allow them to do 3D corrections from within FCP. The plugin called OS3D has been so successful for them for the own use so they decided to release it to the FCP community free of charge. There are no catches it is fully functioning no watermarks etc.
I have used it myself and compared to the other FCP plugins I have used it provides a much better workflow.
The plugin can be downloaded here
http://www.onsight.co.uk/OS3D
