http://fxfactory.com/fxfactorypro/
Flip the source clip to one direction to reveal the incoming clip, or flip the destination clip over the entire frame.
http://fxfactory.com/misc/FxFactoryHelp/pluginguide/transitions/pageflip/index.html
FxFactory is a revolutionary visual effects architecture powering hundreds of plug-ins for Final Cut Pro, Motion, Final Cut Express and Adobe After Effects:
http://fxfactory.com/fxfactory/