This is my first time posting here, but I may have something useful to add. I've found the following to be a good/economical option if you don't need museum glass frames, and don't want to be stuck with the cheap plexiglass in a lot of the lower end frames.
Frame, 18x24:
http://www.amazon.com/gp/product/B003HASC5A/ref=oh_details_o03_s00_i00?ie=UTF8&psc=1
(Comes with thin/cheap plexiglass)
1x$12.76
Mat, 18x24 with 11x17 display area:
http://www.amazon.com/gp/product/B00406184W/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1
1x$8.79
Acid free backing boards:
http://www.amazon.com/gp/product/B003NS4HQY/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1
2xboards, $21.89
Custom cut glass, 18x24:
http://www.lowes.com/pd_20771-405-11824_0__?productId=3121155
1 piece $6.90
Tutorial on photo corners(use acid free paper and tape for these):
http://www.chicaandjo.com/2008/01/15/customize-your-scrapbook-with-handmade-photo-corners/
This particular tutorial show the corners as part of the final display, but you can trim them not to show)
I hope this was helpful, I've found it to be a good way to cheaply mat and frame my pieces. Sorry there are no pics included, but I'm slacking off at the office rather than home.