This time of year brings back-to-school sales, tax-free weekends and first days of school. And while you might have left your school days well in the past, it's never too late to thank a teacher of yours. Whether they taught you how to read, believed in you when very few did, or simply helped you understand basic differential calculus, we're certain that a teacher made a difference in your life at some point. So, harness the magic of Facebook or the Web to find a long-lost teacher. Send them an email full of gratitude. You'll be glad you did.