If you're interested in a long term play (5-10 years) I'd invest in CNQ (Canadian Natural Resources).
Why I'm Bullish on Oil:
There is a lot of debate about how much "easy oil" is actually left on earth, with some people thinking Saudi Arabia is more than half used up. The recent $70 billion stock offering needed by Petrobras so they can develop way offshore in Brazil is an example of the expensive nature of future oil.
The Chinese government has "economic spies" (people loyal to the country that are willing to share info with them) high up in most of the World's major oil companies, and therefore I believe they know more about the World's true oil numbers than almost anyone else out there except for the US military. When oil was $40/barrel during the peak of the recession China signed a 10 year contract with Russia to purchase oil for $87/barrel. China is also developing oil infrastructure in some of the most dangers parts of Iraq. If China, with it's superior knowledge of World oil supplies, is making these moves... I'm convinced that by the time the US economy stabilizes (2012-2015) oil will be $150+/barrel. You've got two countries in Asia (China & India) that each have more than a billion people, and each are going to double their oil consumption in the next 5 years. BUY BUY BUY