Surprised this deal hadn't been posted already.
Goggles4U is offering a 50% off discount on a pair of glasses with coupon code DN50. Shipping is $5.95 for standard (14-21 days) and $9.95 for expedited (10-12 days).
Link to Goggles4U [goggles4u.com]
This is a good deal if you want to purchase a more premium/high end pair of glasses. For example, I just ordered a pair of $20 frames + $33 for bifocals + $15 for anti-reflective + hydrophobic lenses = $68. The 50% coupon made it $34, and with shipping the total was $40.
If you are just looking for a basic pair of single-prescription glasses, you might do better with some of the other coupon codes Goggles4U has floating around.
I have made multiple purchases from goggles4u.com, and I've been very impressed with the quality I've gotten for the price I paid. Over the past 10 months I have purchased:
1 pair of bifocals for $33 shipped;
2 pair of prescription sunglasses for $21 shipped;
1 pair of reading glasses with blu-cut for $31 shipped; and
2 pair of single vision glasses for $8 shipped.
...and just today I ordered the above-mentioned pair for $40. That's 7 pair of glasses, some very basic, some with more high-end features, for less than $125. I've been happy with the quality of the lenses on every purchase, absolutely crystal clear. The frames are just okay, they probably aren't very durable...but at the price, they are virtually disposable anyway.