The Correct Monitor Height
ergocanada.com has a great article on the correct placement, seating, and distance relationships of you and your monitor. Canadians are so smart, helpful, and nice.
HewlettPackard.com , although extremely dry and boring, has an informative article as well which includes some tips on handling glare (which is you have a new iMac wink wink nudge nudge you should read).
As usual, I like to end with something that is fun and informative thanks to superpunch.com: