americanframe.com is good for... frames. I dis-recommend Light Impressions for losing orders and not having things in stock and other problems.
I second americanframe.com. Both times I have placed orders they were promptly shipped and filled. Others may remember back 6 months or so I saw a sale going on there and posted for others to take advantage of it. I believe in the end I paid $3-6/11x14 frame, but I can't remember the exact figure. Look for their sales and stock up!
Let's see what I've got in the magic trash can for Mateo!
My suggestion would be to talk to your local frame shop(s)...
When I was starting out I explained to them that I wasn't stealing business from them, but needed raw materials to frame my own work. (This was work they weren't going to get anyway...)
I ended up meeting a wonderful woman, who eventually gave me a part time job in the shop while I was shooting freelance... Our friendship continues to this day and she is my source for metal frames and hardware.
Mats I get from an art supplier in Toronto... By buying in bulk, I get a discount, and shipping is virtually nothing.
Find out what kind of deals are available to you in your area as well as online... You never know unless you ask... Gives you something to compare to if nothing else.
Aaron Bros. is a large nationwide chain, and they carry N&B for a good price. I especially like their 16x20 with an 8-ply precut 8x10 matte. They have ordered anything in the N&B line for me that they don't usually stock, and it arrives in a week.