This is from apples' site... I just use the gray cloth that came with the display. I've got a client who has to touch the display all the time who I'd like to slap... but I digress...
To clean the LCD:
1. Turn off the computer or display. You may need to turn off the computer in order to turn off some Apple displays.
2. Dampen a clean, soft, lint-free cloth or paper with water only.
3. Wipe the screen. Do not spray liquid directly on the screen.
You may also use a mild glass cleaner that contains no alcohol or ammonia. Most office supply stores sell cleaning kits specifically designed for this purpose.
While there are many commercial products available that will work without damaging the plastics, Apple has tested a product called Klear Screen made by Meridrew Enterprises (http://www.klearscreen.com) and found it does not cause any harm to the plastics. This product may not be available worldwide.
Go to a photo supply shop and get an item they call a lens cloth. Made for cleaning high dollar camera lenses without screwing up the coating. The big bonus is they work great on LCD displays, been using one for years and fairly cheap too. (3 to 5 dollars I think) Also great for glasses. TommyD