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
DF-VFX 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