Canadian Oil Company Stocks

What are some quality Canadian Oil Sands stocks to invest in?
I am considering investing in companies with exposure to the Canadian Oil Sands opportunity. Please provide a list of companies and any analysis or commentary that illustrates the relative quality of each company. Partial answers or answers that relay quality information about a particular stock is okay.
EnCana (Canadian company) may have the heaviest involvement of any oil company in the Oil Sands.
You can find more info. on them here:
http://finance.yahoo.com/q?s=eca
There are many other companies involved, including US majors such as Exxon and/or ConocoPhilips. However, their involvement in the Oil Sands is such a small portion of their overall business, that if you are looking to play the Oil Sands specifically then you are most likely looking at ECA or primarily smaller companies.
Canadian Oil Sands Companies