can you wire up an led to 2 digital pins instead of digital and then ground.
So if you hook up positive to digital pin 13 and negative to digital pin 12. can you set both digital pins as outputs then set 13 to high and 12 to low and the led would turn on. This would allow for more complex led multiplexing.
Yes, you can, as long as you have a current limiting resistor in one of the legs. As you note, that is one way to multiplex an LED matrix.
Yes, low on a pin is equivalent to gnd, so the setup you described is indeed possible.
EDIT (2 seconds afterwords) - I hate it when someone beats you to hitting the "post" button >:(
Thanks a lot now i can start making plans while i wait for my arduino to come in !!! ;D ;D ;D
It was my turn tonight, jezuz. I'm just trying to catch up to your post count. 
Yea... I'm racing ahead, trying to get 500 and become a GOD MEMBER!!!111!!! Take this post for example, completely useless, yet gives me yet another step closer to my goal
There is a nice library for driving multiple LEDS through switched digital pins here: Arduino Playground - Charlieplex Library
Google 'Charlieplexing' for more about this technique