LSrotator - LSRotator lets your iPhone's/iPod's lockscreen rotate according to your device's...
Springtomize - Tear down the walls
Cylinder - Sexy homescreen icon animations
Winterboard - Give your iPhone or iPod Touch a graphical overhaul!
Dreamboard - DreamBoard lets you take control over the homescreen of your jailbroken iPhone.
Five Icon Switcher - This puts more icons into the iOS4 multitasking bar, instead of the usual four.