How to Exit iOS Recovery Mode
iOS 7


Hold down the home button and the lock button at the same time.
Keep holding them down until you see the Apple logo then release the
buttons and you should be finished!


Source: http://www.youtube.com/watch?v=oX9VM590pvo

iOS 6


Download the TinyUmbrella application.
Connect your iPhone or iPod in Recovery mode to your Mac or PC using its USB cable.
Open TinyUmbrella and give it a few seconds until it recognizes your device.




Source: http://www.guidingtech.com/16182/get-iphone-out-of-recovery-mode/