Claymore Sec. has come out with Macroshares and it is supposed to allow investors or "gamblers" to make trades based on the upward/downward price of oil. I am still reading up on it a bit but it is interesting nonetheless. There appears to be some relatively small tracking error and it is an expensive game to play - 1.60 exp ratio - but it could give some investors what they want: the ability to bet on the price movement of oil itself w/o entering futures market. They also use short-term Treasuries as collateral so you can also net some income. Prospectus is available and they also have a FAQ section.
http://www.claymore.com/macro/public/macro/macrohome.aspx
http://www.claymore.com/macro/public/macro/macrohome.aspx