I think oil has great potential as a long term commodity investment, and the current global meltdown will provide a once-in-a-lifetime buying opportunity. However, I think I'll wait until oil has stopped falling and has started to show some sustained gains again - say up from $40 to $50, or from $30 to $40. Buying while it's still within a major downtrend and trying to pick a bottom is too high risk for me ;)
Looks Like It's Time to Buy Oil [View article]
And You Think Today's Gas Prices Are High? [View article]
eg. A plot of the cost to drive 1,000 miles in a the 'average' car for the period vs. per-capita disposable income.