The Heartland Institute is essentially the Tobacco Institute for climate change denial. See previous posts as this blog with the Heartland Institute tag.
UPDATE (February 18, 2012): It appears that one of the documents, the one with the most embarrassing statements, was a forgery--but the statements I've made above all appear to be confirmed.
UPDATE (February 21, 2012): Climate scientist Peter Gleick has confessed to being the leaker of the documents, but claims the apparently forged document was mailed to him anonymously and he scanned it in before distributing it with the others which he obtained by subterfuge after receiving the anonymous mailing. The oddities and errors in the forged document, however, strongly suggest Gleick himself forged the document after receiving the others.