I recently found a very good deal by JC Penney Optical Center. They have been carrying a different special every two weeks that knocks off about $100 off the total price of your glasses.
A friend of mine was able to get prescription glasses that would have been about $250 anywhere else, and he got them for $130 here. That included the anti-glare that's becoming so popular lately. It also included a one-year free warranty for your glasses. If you sit on them and break them, they replace them for free.
Make sure to check your newspaper coupon section or just walk by the store. No coupon necessary and you can always see which special they are carrying by the banner they have on front of the store.