Of the Goggles4U coupons I see come through their almost daily emails the one I find as the best deal is the current one that includes their entire frames collection discounted to $6.95 per pair (plus $5.95 base shipping, valid on one pair per order).
The normal deals are on select lenses but this applies to most of their stock and their more expensive lenses are definitely worth the upgrade IMO. I think this is a better deal for their higher cost lenses than the BOGO option as well, even if doing 2 separate orders.
Coupon codes depend on base frame price:
$9.95 frames use HB995
$12.95 frames use HB1295
$15.95 frames use HB1595
$19.95 frames use HB1995
$24.95 frames use HB2495
*Includes all home branded frames up to $24.95 price
*Free Basic Single Vision Lenses
*Coupon applicable on one pair per order