Reply to How to use a 2nd computer/TV screen with Mac

I've been wondering about doing this for ages, and I've seen it in a lot of peoples studio pictures.
A normal MacBook or iMac, and then a flat/widescreen TV or another mac I'm not sure.

Like in this video http://j.mp/WhWiD2 at about 3:20, he has logic open, he drags a file over off the screen and into Traktor which is running on another screen...

How do I set this up? I have a MacBook Pro, and a mac g5 power PC,
If I can't do it with my g5 mac I can buy a cheap little flat screen TV to hook it up if that's what I need.

Can I do it with my mac g5? If so how would I do it/what cable or program is needed?

And how would I do it with a TV screen??

Thanks!