I found that both the Voxengo Elephant and Soniformer plugins have become an invaluable addition to my mastering setup. Elephant helps add that extra volume without adding the squishy sound of some of the other tools out there. And Soniformer is a fantastic dynamic EQ... I can't live without them...
George Leger III - Juno Award Winning Mastering Engineer, and author of VTC "Logic Audio 6" training CD.