Well, one thing that helps, even though it is not really free, is tax free weekend. In Alabama, it is the weekend of 2 - 4 August 2013. If you need to see what is included, here is the link: 2013 Tax Holiday.
Staples Teacher Back-to-School is event is also in August. The Staples in my town will have their event on 10 August 2013. They also start all of their back to school sales on 1 July 2013.
- I go every year. Usually the bag has some needed small supplies. Last year it was paper clips, highlighters, thumbtacks and pencils. Also, they usually have penny and nickel sales during the back to school sales. Teachers can get up to thirty of each item where I live.
Office Max also has Teacher Appreciation Events planned for August. The one closest to me is 3 - 5 August.
Poetry Month (April) Posters. I have been receiving these since 2005. The kids love to see them go up. Students that have moved beyond my classroom, will come visit to see the new poster. Academy of American Poets Poster
I am a member of Freecycle.org. All kinds of stuff can be found free. It is offered and can be requested. I have been on both ends of this exchange, and I have not had a bad experience. As with all things, make sure you meet in a safe, populated area to receive any items. Freecycle Main Page
I will probably update this post as I find items that I can use.