UPDATE: (Sept. 2014) – Netflix will soon natively support Ubuntu, there are only a few small hurdles remaining, likely to be resolved by the NSS update expected in Ubuntu 14.10 (Utopic). A workaround is available for the impatient… http://www.omgubuntu.co.uk/2014/08/netflix-linux-html5-support-plugins.
For various reasons primarily related to DRM, there is not a native Ubuntu/Linux viewer for Netflix… this is one of the cases where WINE can help you out by providing (not emulating) a Windows environment.
These commands are for the Ubuntu setup, similar steps for other Linux distributions are available in the references.
I’ve found that it is better to pre-install the Wine Gecko and Wine Mono packages on Ubuntu.
sudo apt-get install wine-gecko
sudo apt-get install wine-mono
sudo apt-add-repository ppa:ehoover/compholio
sudo apt-get update
sudo apt-get install netflix-desktop
If you’ve never used WINE before within your Ubuntu/Linux environment, you’ll likely need to let it download the extensions for Windows, I believe that it will request to download and install the Gecko and Mono packages described above, click "Yes" if asked and all should go well!