The American Film Institute has come out with an updated list of the greatest American movies of the last 100 years, for the tenth anniversary of the first list, and I've already seen all of them! It's a very good list, better than the one they did in 1996. I recommend it as a minimum for every Netflix member. Netflix has a link to the AFI list, but it's broken at the moment; perhaps because they are working on the new list. :)
UPDATE - the link is working again, and the Netflix site has been updated with the latest AFI 100 Great Movies. Four on the list are not available on DVD.