For those of you using unblock-us.com, there is now (well, three weeks ago), a feature to let you switch between Netflix catalogues. You can use US one minute, then Canada, the UK, etc.
When I was in the UK in March, I noticed that "It's Always Sunny in Philadelphia" was available there but not on the US or Canada Netflix. And some shows like "Community" and "Degrassi" (yeah I'm 33 and I like Degrassi and I don't care what you think) are only available on Netflix Canada.
So here's how to switch between catalogues:
http://support.unblock-us.com/custom...o-watch---beta
You'll need to log in with your browser, but it is easier than switching your DNS servers to toggle between Canada and US versions. Not to mention you can also browse some other countries too.