Tom, I'm not sure what type of glasses you have (single-vision, bifocals, etc), but for single-vision glasses, I've been very happy with Zenni Optical ($7-$8 for frames + lenses, + $5 for anti-glare, + $5 for shipping for the entire order. Want them to be prescription sunglasses? Add $5.) You have to get you pupillary distance measurement from your eye doc (sometimes you have to insist on it). Bifocals or those transition bi- and tri-focals might be more difficult to get absolutely correct in terms of measurements, but frankly I've had brick-and-mortar places screw that up.
I don't recommend their light-to-dark transition lenses--for me, theirs don't go nearly dark enough. But their lenses & frames have otherwise worked beautifully for me and they are cheap enough to allow me to buy a spare pair of eyeglasses.
(Just FYI. I promise, I don't get any kickbacks from them. ;-))