Commodities, Commodities, Commodities:
A few general words about commodities. Perhaps the most risky, and conversely the most potentially profitable oil investment, is oil futures trading. A futures contract is an agreement to buy so many barrels of oil, at a set price, on a set date. If you know the price of oil is going to be way up a year from now, but you can lock in today's prices with a future contract - well, you see how it could work.
The major obstacle to futures trading is up-front cash. Unlike stocks, where you can open and fund an account online these days with as little as $500-$1000, most commodity brokers are going to want a significant deposit of $5000 or higher. But if you have courage, money, and a keen trading sense futures are definitely an option.
While no investment should be made without extensive research, betting that the black gold is going to get more golden is an idea with strong fundamentals backing it.