Obviously, I'm in the same boat as you. Usually, I order Xbox USA games from
Tronix. They're based in NY, they offer a great service. For 15 $ you can get your games shipped with FedEx, they arrive in 2 days and you can track them. This will be the third year I order NCAA/Madden from them, never had a problem. Last year, I even got NCAA 2006 on the US release date, because I had pre-ordered.
It's, like, about a month that I check the site every day, searching for the Head Coach pre-order, but they still don't have it. I really hope it will be available soon.
As for other sites, I know EB Games and Gamestop offer international service, but they want 25 $ only for shipping, and I don't know how much will it takes for the games to arrive. Also, check out
DVDBoxOffice, Canadian site. I know it's very reliable, but I've never tried it.