Cylinder - Sexy homescreen icon animations
LSrotator - LSRotator lets your iPhone's/iPod's lockscreen rotate according to your device's...
Winterboard - Give your iPhone or iPod Touch a graphical overhaul!
Springtomize - Tear down the walls
Five Icon Switcher - This puts more icons into the iOS4 multitasking bar, instead of the usual four.
Lockinfo - You can find this app in Cydia - Tweaks.