I wanted to share my two free plugins for After Effects:
This contains two selection plugins allowing you to select pixels based on their Alpha and Luminosity values, and a Despill filter - I think it's better than the AE built in one
This plugin let's you select up to five objects using a Node ID/Object ID pass and also remove edge artifacts that can occur when you do it.
Hope you find them useful.
PS. Download link is in the movie description.