Using this app you can put icons anywhere in the folders and on the grid. This tweak also allows you to shut down your iPhone like a TV. You should note that no icons will be added to your iPhone homescreen by this tweak. Simply go to iPhone settings.app to configure this tweak.
Springboard Enhancer is available in Cydia under BigBoss repository for free of cost. You will need to have a jailbroken iPhone to install this tweak. If you don’t have jailbroken iPhone then you can follow the step by step instructions posted here to jailbreak your iPhone on iOS 4.2.1 with Redsn0w.