AllPosters.com is currently running a special on their site for 15% off almost all items. They have not only Twilight posters but also New Moon posters.
Here are just a couple of items on sale:
AllPosters.com has an entire Twilight section. They have Twilight posters, Twilight standups, framed Twilight art, Twilight shirts, and more. They also have the only New Moon movie poster that is currently out. If you use the coupon “SUGGE” by tomorrow, you will get 15% off. If you are reading this post too late, click on the link below anyway and see if there is a banner on the page at the bottom with a new discount. They seem to change every couple of days.