VolumeBooster, a fairly old tweak that allows you to increase the phone's volume by 20% above the maximum limit imposed by Apple, has been updated today to version 4.0 and is finally compatible with iOS 4.0. The tweak works only through the Winterboard application, so without it you can make absolutely no changes. I personally have not tested this tweak, although the iPhone's sound is quite weak, practically if I walk on the street (even without much traffic around) I can barely hear it when it rings in my pocket and I have the volume set to maximum everywhere.
VolumeBooster 4.0 is available for free in Cydia.
