Old DNS codes to connect to American Netflix from outside the US (for things like troops serving in the US military) have stopped working, but here are updated ones:
Update Oct 8, 2013: The old codes are still reported as working for some users, though if they don't work for you, read through the comments below for more. If they work/don't work for you, you can post anonymously to help others get working codes.
Update Oct 19,2013: Kevin24 in the comments gives this DNS that is working for some people, try it out:
Update Nov 19,2013: Checked the below code for Canada, still working via MediaHint. The old code was just also reported to be working in the UK.
Old code, may not work:
If you don't know what this is, you probably don't need it. If you're having trouble getting around Country Restrictions on Netflix, click the link on the left to learn how to do it.