If your iPhone gets stuck in iTunes DFU Recovery mode  – possibly due to trying to upgrade a jailbroken iPhone to a regular  iTunes iOS upgrade (which you can’t do),  there are a couple of tools to get it out of recovery mode DFU.

Get the latest Redsn0w   — Mac OSX redsn0w 0.9.10b6b  or  Windows redsn0w 0.9.10b6b

Before you try the tools its worth a try a manual try on the iPhone – hold the power button for 15 secs – then boot by holding the home button – if that doesn’t work try the below.

– Quit iTunes

– Launch redsn0w and click on Extras

 

– Connect the iPhone

– Click on Recovery Fix

 

– Connect the iPhone and follow the remainder of  the onscreen instructions.

 

Another tool with an exit recovery dfu mode is Tiny Umbrella

– Quit iTunes

– Connect the iPhone

– Launch Tiny Umbrella and click on either ‘Exit’ or ‘Fix’ recovery

 

To upgrade an previously jailbroken IPhone to iOS 5 and preserve existing baseband check here.