A clever gent who goes by the name SeventhSon (we hope in reference to the totally ripping Iron Maiden record Seventh Son of a Seventh Son) has discovered a method to alter both the DVD key and game region code on Microsoft's Xbox 360, at least for the Hypervisor exploitable 4532 and 4548 kernels. If you're not sure what that all means don't feel bad, part of this hack involves desoldering your Xbox flash chip -- something most of us aren't getting around to anytime soon. However, for the tenacious and technologically handy, this opens up all kinds of diabolical possibilities like, um... playing UK games on your US Xbox.
Update: In addition to clarifying the debate over his name origins, SeventhSon has posted this update to the comments below: Another clarification. This hack will work on all kernels, not just the HV exploitable ones. As long as you obtain the cpu-key before you upgrade past version 4548. This way you can run the latest kernel and still modify your game region code.