Where do I find the #IMEI code?

On many devices, the IMEI number can be retrieved by entering *#06# or is located in the battery compartment.

Android : Settings –> About Phone
iOS : Settings –> General –> About
Sony Ericsson (New Devices) : Options –> status.
Sony Ericsson (Old Devices): Dial * Right * Left Left * Left
Blackberry : Options –> Status