My usual go-to place for frames, glass and matting is Hobby Lobby, locally in Prescott, AZ but stores everywhere in the U.S. Frame prices tend to be a little high, but every other week the store goes into a store-wide, 50% off sale. You have to be careful when buying frames because the quality varies from time to time (warping, scratches, etc.) But, overall, They're reliable.
And, no, I don't work for them, just a usually happy customer.