Educents is similar to Groupon and Amazon Local. The only difference is that it focuses only on educational products. They are offering a promotion for Teacher Appreciation Week (see below).
Give Your Favorite Teacher(s) $5 - Whether it's your Mom, your Classroom teacher, your Grandparents, your friend or another special human being who taught you important lessons, thank them by giving them a free $5 gift card, on us! Check out Educents. * I am not sure how long this will last.
They have been in business about a year. I have gotten an online subscription to a teaching pay site for $5, so there are some cheap things.