RTFA: http://www.usafis.org/faq/land_english.asp

Green Card Lottery
US Green-Card Application Service
Visa USA

USAFIS organization invites you to participate in the American Green Card Lottery program where you may win a green card and live and work in the United States. If you are not an American citizen, you must join the program and take advantage of the opportunity that has been offered to you by a program of the American government, through a law that has been passed by Congress - the “Diversity Green Card Lottery” program.

I found this after clicking on an advertisement in a news article (wow! ads work sometimes). I thought it pretty odd that they are giving away green cards in a raffle and I’m not really sure what the point is of holding this lottery. Anyone have any thoughts on this?