Speed Up iPhone 4 / 3GS by Speed Intensifier

Speed Intensifier is a new free tweak available on Cydia which allows you to speed up your iPhone performance by removing iOS animations which happen in every action you do on your phone such as opening folder or window.

How to install  Speed Intensifier :
 

Speed Intensifier is a 2-part tweak, one for your Setting.app and the other part is a Winterboard.  
Speed Intensifier is available via insanelyi.com repo, you have to add this repo to your Cydia,

Open Cydia > Manage > Sources > Edit > Add this rep “http://repo.insanelyi.com”
search for Speed Intensifier. 

You will see the app as well as the Speed Intensifier Addon, it's recommended to add both of them.

The add-on’s description states that it breaks the limitations that Apple imposes on the device to save your battery. It will make your iPhone’s processors operate as if it is plugged into the wall charging.

You can easily adjust Speed Intensifier from Setting app, so you can change speed of the tweak or disable it. By the way you have to know that the app developer claims that the app doesn't drain your battery. Give it a try now, it is free.