Atom posts a look at his new Addon for Blender, RE:Group, which is an advanced group manager that can offset animation in groups from group participants.
It will essentially manage a link between a group and a particle system in Blender, allowing you to animate groups of particles based upon the particle birth time.
This video demonstrates the RE:Group AddOn for Blender 2.68. RE:Group manages a link between a group and a particle system
Atom notes that part of the management tasks are to calculate the offset animation from the source group to the cluster that will place the animated object. This will allow you to delay animations until a particle is born.