Staples is doing their teacher thing this coming Saturday. I think they'll open at like 8 AM. They usually have really nice goody bags, some breakfast items and some discounts. I know Office Max and Office Depot do the same thing but I haven't heard about theirs yet.
Also, the Barnes and Noble in Southlake is having a school open house this Saturday starting at 1 PM. If you have a teacher card (from them), then I don't know that you get anything by going, although they are going to have some prizes. However, if you don't already have a teacher card through them, it's free so I would go sign up for it. You need your ID badge. Their card will give you 20% off purchases "for your classroom". However, I bought my travel books for Disney and got the discount.