Buy factory direct from PictureFrames.com. Metal, custom and ready-made picture frames, mats, tools and more.
Art Media was my favorite source of framing materials, whether online or off. It was a small local chain based in Portland, Oregon. The company Dick Blick purchased Art media in late 2011. I don't have enough experience one way or the other to comment on Dick Blick yet (January, 2012). The link above now goes to the Dick Blick site.
