I read an article in a magazine not too long ago that referenced Zenni Optical as a good place to get inexpensive prescription glasses. Most of their glasses are either $8.95 or $12.95 for the frames. There's no additional charge for the lenses, unless you want anti-reflective coating or tinted lenses (I think both are $4). This site was perfect for me because my prescription has expired, but I also know that it hasn't changed enough to make me want to shell out to visit the eye doctor when it isn't covered by my insurance. I ordered these glasses in white with full-tinted lenses to use as prescription sunglasses this summer. Who can beat the price?
The only major downside is that it literally took about 3 weeks for my glasses to arrive, and there's no option to select expedited shipping. I also thought it was odd that they don't give you any tracking number or time estimate when you place your order--I didn't receive a tracking number emailed to me until AFTER I had actually received the glasses!
It was also a little bit hard not being able to try on the glasses before purchasing them. The sunglasses aren't quite the shape I thought they'd be, and aren't the most flattering shape for my face, but honestly...I don't care. It's really nice to be able to see while I drive, and that's the most important!
Really, the place that I think this website is exceptionally helpful is with kids' glasses--they have a great selection of frames, and although most of the kids' frames are in the $20 range, that still sure beats the $100's I know would be spent buying through the eye doctor.