If you live in the Twin Cities metro area of Minnesota, listen up: Free kids eyeglasses (frame and ultralight lenses) for kids 12 and under at Eye 35 Eyecare in Lakeville.
The eye exam must be done at Eye 35 Eyecare by Dr. Fontana or Dr. Bell, and they do take most kinds of insurance for the exam. They claim to have a great selection, too. Some restrictions apply, so ask an associate there for details.
This offer runs through the end of August, so be sure to sign up for an appointment soon. (Thanks to Kiera, for the tip!)
If you don’t live in the Twin Cities area, and are still looking for affordable eyeware, try Zenni Optical. You can get frames for as little as $8 and while I haven’t tried them myself, several friends and Money Saving Mom have said good things about them. It may be worth trying if you’re on a tight budget!