Boasting an impressive 17,000+ movie poster archive, Impawards.com positions itself as one of the largest repositories of movie posters online.
The idea of the site is basically to give an annual award to the best and worse movie posters of the Hollywood industry, and to highlight best and worse taglines, bizarre and funny occurrences of design artists. The archive includes some arty stuff and a respectable international selection, but it rather sticks to the US commercial industry, but hey, they do it very professionally and very thoroughly. You can look at reasonably sized images (A5 and A4 sizes), and get linkage to sites that get complete data on features movies, and where you can buy the posters (they are the experts, so you should probably rely on what they have to say on what the best stores are). Regarding the awards in themselves, well, you might not share their criteria, but at least you get to remember some really good and really bad films; winner of best poster for 2006, for example, was Hard Candy, seriously… 
