Fastsnap is an application that lets you use iphone's volume buttons as a camera shutter button. It can also mute the shutter sound while taking a photo. No more searching for the button insede camera application just use the volume buttons inside camera app or any other app that has camera functionality. Fastsnap can be downloaded with $0.99 from Cydia, where there's also a free cracked version.
Just check it out Start from $0.01 for real.