If you’ve ever got your PIN code wrong too many times and got your SIM locked, you were probably as surprised as I was when Android gives you no option to unlock the phone! Fortunately there’s an answer.
To unlock your Android-based device go to the Emergency Call screen and enter in the following (replace the angled brackets with the appropriate info):
So for example:
As a side effect this should work on any SIM-containing device at a screen where you can enter phone numbers, not just devices running the Android OS. As of writing, Android-based devices are the HTC Dream (T-Mobile G1) and HTC Magic.
And make sure you keep your PUK code secret — anyone can override your PIN with their own using it!
Thanks to theWeir for posting that solution.