Great guide. If you are into these sort of guides of how to deal with the US government I have written a couple for the W8-BEN-E form [1] (you need this if you have any US customers) and also for registering to do business with the US government [2]. These are biased towards Australians, but they should be helpful for others too.

1. http://www.tillett.info/2015/06/20/how-to-complete-w-8ben-e-...

2. http://www.tillett.info/2015/12/01/how-to-register-an-austra...