The Fracture Modifier is a system to interactively destroy and physically simulate the shards of objects in an easy, performant and non-destructive way. This allows you to shatter and simulate the objects as you like while the original geometry of the object remains untouched and intact.
BlenderArtists.org support forum thread
BlenderPhysics Hosted Fracture Modifier Builds
Kai Kostack Hosted Fracture Modifier Builds
BlenderWiki page about Fracture Modifier
Development and experimental videos from the fracture modifier build & helpers addon by Dennis Fassbaender
Simulation Videos made by Kai Kostack