1. Matrox Triplehead2go Analog Edition Mac Software Free
2. Matrox Triplehead2go Software

Make offer - Matrox TripleHead2Go Digital Edition Triple Screen Graphics Card Pc or Mac Matrox TripleHead2Go Digital Edition (T2G-D3D-IF) WITH 3 x DELL FP817 19' DISP.

You could also have tried DisplayLink-based hardware. Their Mac support is good and I'm running two additional displays from my MacBook Air with zero problems.
There are plenty of vendors supplying hardware:
http://www.displaylink.com/shop.html
And good Mac drivers (with some 3D acceleration limitations):
http://www.displaylink.com/support/mac_downloads.html

Or use any old computer and Screenrecyler. The refresh rate on the screenreclyed monitor will be pretty low and whether and how you get it color-calibrated I don't know. But for a lot of situations it works absolutely fine.

Matrox Triplehead2go Analog Edition Mac Software Free

Cool hint!
I'm just now considering to switch to almost exactly this kind of setup, also with two 1600*1200 DVI displays but in my case with an older MacBook Pro 17' (first Core 2 generation) which still has a native Dual Link DVI output. But it is interesting that it even works through the DisplayPort-to-DVI-Adapter with the new ones.
I just hope the cooling issue will be less pronounced in that case; When the external GPU in the MacBook Pro really gets to work, the machine can get a bit noisy. But since the GPU has its own fan in the MacBook Pro and the case is significantly larger, I hope cooling will normally suffice without ramping up the fan speed. How is fan behaviour with a 30' display connected, especially together with the internal display? Any experiences? It should be roughly comparable with two external 20' ones regarding GPU load.
I would probably use all three displays in that case since I don't want the menu bar or the Dock on my main screen(s).
Another question: I guess since OS X doesn't know about the separate external displays, alerts and other dialogs will pop up exactly across the division between them, won't they?

Matrox Triplehead2go Software