iCubie in iMovie 2011's Capture Window
By default, iMovie 2011's capture window will only acknowledge certain webcams. To change this:
Open the Terminal app, which is in Applications/Utilities.
Copy and paste this line into the Terminal window and press return:
defaults write com.apple.iMovieApp allowUnsupportedWebcams -bool YES
Re-open iMovie, and you should now see the iCubie listed.
Sorry, but this does not appear to work in the new iMovie 10.x.