I was able to sell the curriculum that I used last year for 5th and 10th grade and the very nice surprise was that it sold for more than I paid for it! Can't beat that with a big stick.
I also found a really nice book called, The Kids' Guide to Digital Photography: How to Shoot, Save, Play With & Print Your Digital Photos on E-Bay for under $2 and it is in excellent, almost new condition. I think 6th grade will really enjoy using this book and the surprise "back-to-school" gift that I purchased. Every year I try to get a small gift for each student since I save money on the whole back to school clothes and supplies thing.
