http://en.wikipedia.org/wiki/Delayed_ejaculation
I can't believe I forgot to ask about anti-depressants? I know that they delayed my orgasm. Also, exercising can help. Blood pressure plays a role I think, but I have no way of knowing for sure.
http://greatsexgames.com/forums/showthread.php?t=871
Here is another forum with this same issue. You might need to register, but if you are interested in some other ideas, they are here.