I used to have the most oily skin out there, a lot like how you say yours is, if not worse (would have high shine within 20 minutes at one point). At its worst, I was taking Alesse (oral contraceptive) and it seems this was contributing significantly to the problem. I went to see a dermatologist and she perscribed Yasmin (another OC). This pill blocks androgens (which can cause oilyness in skin), yet I did not see much improvement. Besides that, messing with my hormones that way was a disaster (weight gain, reduced sex drive, mood swings, no energy, depression, panic attacks and anxiety, I could go on...) and I would recommend that if you decide to try a pill, approach it with great caution.
3 months ago I went off all forms of hormonal birth control, and my skin is better than it has been in YEARS. Not to mention that all the other problems went away. I was really amazed at how much better my skin got going off the pill, especially since it's expected to help your skin (especially the one I was on). Just something to consider if you are taking one.
Aside from that, I have had success with the following:
(*) Clinique's facial soap in '3' (oily skin)
(*) Clinique's Clarifying Lotion in '4' (for oily skin), whiped on face after washing (probably the most significant on the list)
(*) Next, applying Clean and Clear persa gel (benzoyl peroxide cream, which is water based, alcohol based is TOO much) to entire face
(*) Using a lightweight oil-free foundation. I am currently using MAC's tinted moisturizer and am liking it. I have used Studio Fix Fluid but find it makes my face shinier.
(*) For a powder, simply applying MAC's Blot Powder all over the face.
A lot of people say that mositurizing works for them, and not to dry the skin too much (and I am sure would be horrified with all I do to dry it), but hey, it works for me (and I have tried not drying it out too). Just throwing that out there.