The following worked for me for unlocking the Cingular BlackBerry Pearl I recently got:
- Figure out your IMEI number. Press *#06# to find it.
- Go to unlock8800 and pay for your unlock code. Mine arrived via email the next morning. I paid $20.
- Use the instructions here to enter the unlock code. The instructions you get from the unlock8800 guys aren't too clear; you don't need to press each key for MEPPD and MEPP2 twice; ie. to get the letter P you push the [OP] key just once.
- Note that when you first go the "SIM Card" page you won't see what you type, but once you enter MEPPD correctly you'll see a menu.