I found this one out goofing around. Its very easy to do. Make your Netflix account (if you don't have one). Then click on your account. After that click on your Netflix ready devices and computers. After that you click on Activate a Device. As you can see I already have 2 360's connected to one netflix account. After that on your 360 boot up Netflix and go to I have an existing Netflix account. A code will pop-up. Type the code in the box on the PC. After that it will activate on the 360. This is especially nice for the 360 update that was released today. You can give this to friends. (A TOTAL OF 6 DEVICES CAN BE LINKED TO ONE ACCOUNT.)
They really should release Netflix in the UK. Even if its just for streaming I'm sure lots of people would be very glad.