Pop sockets! DD is going on a school trip to DC next summer, and we have been selling pop sockets with the school logo and the school saying (EFND - Eagle Fight Never Dies) at the school open houses. They are selling like hotcakes. We have both pink and school colors, and the pink aren't selling well at all. Most kids are buying school colors.
At one of my daughter's school, nike-style running shorts with the school name at the lower edge of the short were very popular. You don't want bulk, but hoodies are the best selling.