For what reason? your posted pic tell it all... 10seconds while on itunes and you'll be prompted....

Can also be used in 2.0

I remember there's an app that allows you to put your phone into sleep mode if your sleep/wake button is spoiled..
But I don't remember the name

im sure u wanna do something with ur phone(upgrade FW mostly)
well, u can try DFU mode if u wanna performe upgrade/ downgrade FW

Be wary that there's a difference between Recovery Mode and DFU Mode . The steps to get into these modes are also different. The differences are :

Recovery Mode :
- Done by holding Home button while connecting the dock connector
- Screen will display iTunes icon and the USB cable connector
- Can be reversed back to normal mode using certain command lines or applications like iBrickr and ZiPhone

DFU Mode :
- Done by FIRST docking the iPhone, then holding both the Sleep/Wake & Home button for 10 seconds, before releasing ONLY the Sleep/Wake button and continue holding the Home button until your Mac/Windows PC sounds an audible beep signifying a new USB device
- Screen will display NOTHING, as if it were switched off. iTunes will still recognize it in 'recovery mode'
- Cannot be reversed or kicked out of, MUST be restored in iTunes

Hopefully this helps clarify any confusion which may have been on anyone's minds regarding the 2 different modes.