Sebastian Koenig shows off some recent developments already in the Blender Trunk demonstrating some new Masking functionality in Blender 3D. This video provides a pretty good overview of the masking workflow that is being added to Blender for the Mango Open Movie Project.

Michalis Gkiokas also takes a look at using the new Masking tools in Blender in his latest tutorial tracker assisted Masking in Blender:

Sebastian Koenig writes:

This is a first demo of the current status of the masking tools in Blender, that are currently being developed. Since we need it desparately for the work on Mango, we are all very happy to be able to use these tools.

But be aware that the development is still in progress, so you can expect some changes and improvements.
These tools have been merged to the main development version of Blender, so if you want to use them, either build trunk (SVN), or go to graphicall.org and download the latest version there.

Thanks to Sergey Sharybin, Pete Larabell and Campbell Barton for their work!