Misunderstanding - yes Two 30 Inch on Macbook Pro 2007
It appears that there are some misunderstandings here. Some people think that the question is running two (dual) 30 inch monitors, from the one dual-link DVI port on the Macbook Pro 2007. Nope. What the poster wanted to know was how to make two 30 inch displays (dual 30-inchers) work with the 2007 Macbook.
What is true is that you need a dual-link DVI connection for each of the 30 inch monitors - i.e. two dual-link DVI ports (you can count that as four DVI ports in total, if you like).
The Macbook Pro 2007 has one dual-link DVI port, which will run one of the 30 inch monitors all by itself. So what next? How can you add a second dual-link port for a second 30 inch monitor?
As other posters pointed out, the magic is the ExpressCard/34 slot on the side of the MacbookPro, in tandem with the dual-link DVI of the Macbook itself. You can plug an extra-30-inch monitor card into that ExpressCard/34 slot, giving you a second dual-link DVI port.
How it works:
1) Apple Cinema Display 30" #1: use dual-link DVI output of the Macbook Pro 2007
2) Apple Cinema Display 30" #2: use dual-link DVI output of the VillageTronic card, plugged into ExpressCard/34 slot on the side of the Macbook Pro 2007
Here are the tech specs of the Macbook Pro 2007 (showing the ExpressCard/34 slot):
http://support.apple.com/kb/SP13
Talk to Villagetronic - they will confirm this setup and happily sell you a card.
Now, on to the next thing - the 2009 Macbook Pro. Now, with the very latest hardware ... you are up the creek without a paddle.
On the 2009 Macbook Pro, the mini displayport will allow you to connect a dual-link DVI adapter. And then ... you're out in the cold, the very wintry, bone-chilling cold. The ExpressCard/34 slot is gone, gone, gone.
In theory, you could use a USB monitor adapter, such as the Kensington Dual Monitor Adapter, the Tritton SEE2 Xtreme, the EVGA UV16+, or the OWC USB to DVI/etc adapter. Problems: None of those will support a dual-link output, and none of them support more than 1600x1200 / 1680 x 1050. Moreover, none of them support Quartz graphics, kiboshing much of your OS X graphics. If you plan to display text-only on the second monitor, you could run a 19 or 20 incher.
Sigh. So the 2009 Macbook Pro is one giant step for humankind backwards, in terms of multiple monitor support. If anyone can see a way round this, let me know - I want a new Macbook and I'd like two 30-inch displays!
Summary:
2007 Macbook Pro - get the Villagetronic, enjoy two 30-inch Cinema Displays
2009 Macbook Pro - learn to live with one 30-inch Display. In terms of the respect you got from the design "upgrade", you have been demoted from Fleet Admiral to Supply Ship Refueler, Class III. Maybe check out the new Mimo 7-inch USB display as a second monitor ... you could park your cursor there so it doesn't distract you ...