the NYMEX trades those.
www.NYMEX.com
However, it doesn't really matter. What you need is a broker to give you access to those products and then they take care of the routing.
However, however, you will probably get a much better deal in spread and commission costs by trading an Oil ETF like USO. That will give you all the benefits you are probably looking for but with smaller chunks and less cost.
However, however, however, if you really want to "get jiggy" with it then may I suggest DIG, which is a leverage oil ETF with options. Think about that - Leveraging options on a leveraged ETF... how cool is that. Once again you will probably save in costs and be able to control your position size more effectively than options on CL.
Just food for thought