I use a display link adapter on my macbook pro to drive a third screen. Works just great (there was a bad patch with driver installs in one of the later leopard versions but no problems with Snow Leopard).
You can even play video on it
You can even play video on it
I thought having two external monitors for a MBP was either not possible or pretty expensive. This dongle seems to say it's neither.
It doesn't seem to be widely known about - I only found out about it from comments on a forum - so I'm returning the favour :-) . Its made a big difference to my setup.
Screen 1: Laptop Display Screen 2: 23" Apple Cinema Display via on-board DVI Screen 3: 22" LCD or 60" Plasma (depending) via USB/DisplayLink