I own a macbook for 2 years now and only a few months ago I needed to connect my Macbook to an external display “only”, meaning that I want to close the laptop lid and work on a huge external display with an external keyboard and mouse to save the screen and to enjoy everything in a one big screen (I love dual-head too but I hate it when one screen is much bigger that the other).
So, for quite sometime I thought that this is not possible, but it turned out to be possible and pretty easy to do.
Now to the important part 
You MUST connect all of the following things first;
- MagSafe.
- External Display
- USB Mouse and USB Keyboard
then close the lid, you will get the system sleeping as you usually do, then click on the mouse and the system will fire up again and shining on the external display 
It’s a trivial trick but it took me quite sometime to discover and I tested it only on Macbook pro and snow leopard, however, it should still work on any other macbook I suppose.
Ahmed Soliman Farghal is a professional "Software/Systems" engineer with exceptional computer science background and spectacular record of projects and achievements.
yes it does work with macbook too, and it’s really great as u’ve mentioned.
Having one big screen is better than moving my eyes between the large one and the real small one -relatively-
nice trick that i love
seems Interesting
Could you use resolution higher than the one used in your MacBook when you are connected to the external display?
For example if the max resolution in MBP is 1440×900 could you use higher resolution when you connect an external display?
Yes, as it supports connecting 29″ apple display, it works perfectly using the native resolution of my external display 1920×1080