Digital Juice sells a series of animated backgrounds that they call Jump Backs. These are broadcast quality files and are apparently used in commercial productions like MTV and American Idol.
Ulead has the Jump Backs volumes on sale at 2/3 off the normal prices. A different set called Motion Backs is also on sale.
Sony sells something similar that they call Vision Series. Not as extensive, but at about the same price ($80 per volume).
All of these are royalty free and will work with any editing software that can handle DV AVI and QuickTme files.

