This site has a great collection of posters of classic films. Here is a selection of classic film noirs.
Poster above via Dave Kehr's blog. I am glad to see Richard Brooks' "In Cold Blood" being selected for preservation. I saw it once on big screen and it was an unforgettable experience. Gripping and actually quite frightening. Surprisingly it is not very well known, even after the success of the recent films about Truman Capote.