Free Glasses from Firmoo (US), Just Pay Shipping
Firmoo is a US based optical store, that ships worldwide. And they've just re-launched their free eyewear promo, in which you can claim a free pair of prescription glasses, and pay only the shipping fee!
Now, just note that this offer does not apply to designer glasses, just their regular stock. When you are browsing the glasses, you will see a "get now" link towards the top left of the page - click this, and they will issue with a one-time use coupon code to use on your free glasses. You must use the coupon code within 2 hours, so be ready to order there and then. If you want to pay extra for customisation like different types of lenses, or added extras, you can do so... but the basic pair of glasses will be free.
I tested the deal out on a $20 pair of prescription frames, and it discounted them to zero. The shipping cost was $12.95 to Canada, which is really quite reasonable. You can even pay by paypal, if that's handier for you.
I read that Firmoo only give out a certain number of free pairs per day - so if you cannot see the "get now" link on certain frames, maybe check in daily to make sure you get your freebie from Firmoo.