I've been buying frames online for about 8 or 9 years. Then I would have the prescriptions filled at my local Walmart optician department. I've generally been satisfied.
I originally bought new old stock frame samples from a German frame store on ebay. They had a wide and diverse selection from several European manufacturers. You could get classy or weird, cool or eccentric at prices from about $10 to $200. Shipping was inexpensive and well packaged. That store now seems to be inactive.
My last purchase of three frames was from the Egamon store on ebay:http://shop.ebay.com/egamon/m.html
Their range of styles is not as extensive as that of the German store, but I found good frames for $20 to $30. I was satisfied with the quality and shipping.
The Walmart optical in-store professional section measures how far apart your eyes are, traces the shape of the frames and sends that info and the prescription off to off-site lens manufacturer. They get the lenses back in about a week and put them in the frames. They charge you an extra $10 if you bring in your own frames instead of buying what they offer. Regular thin, single-vision lenses cost about $50. This time I also got prescription (distant/driving) sunglasses with polarized lenses. The sunglasses lenses cost $90. I am completely satisfied with the result.