Barrel by Aaron Ash ($2.99)

If you've ever used Linux, you might have seen or heard of Compiz which, when setup for it, will allow your desktop to be displayed on a rotating cube. The default animation for iPhone is boring, the pages simply slide off the screen. Yawn. If you want to add an exciting new animation, install Barrel!

Here's how:

Open Cydia and choose "Search", find Barrel by Aaron Ash and install it. Re-spring and go to your iPhones settings menu. Choose Barrel and then select the mode (animation) you want. I suggest "Curl and Roll Away", though the 3D cube (both inside and outside) are available as well for a total of 17 animations (as of version 1.5.7).

This has to be 'the' top modification to the Springboard that I've found so far. Thank you Aaron Ash!

Cydia Store Link (iDevice only):
Barrel