Amazon just launched a complimentary service, Amazon Ignite, only instead of sharing content, teachers can use the new service to sell their content to other teachers.
Where Amazon Inspire is a standalone site, Amazon Ignite is a part of Amazon.com along the lines of KDP, only with fewer restrictions on content, and also with better payment terms. Teachers can upload and sell Word DOCs, Powerpoints, spreadsheets, PDFs, and even ZIP files. They'll earn a 70% royalty on all sales, except for items priced under $2.99, where Amazon charges an additional 30 cent transaction on each sale.
While Ignite is focused on teachers, the content is sold on Amazon.com, and is available to all. The selection can be filtered by grade level, topic, resource type, and educational standard across areas such as math, social studies, technology, science, and language arts. Amazon offers previews of materials with its "look inside" feature (just like in the Kindle Store), along with recommendations and customer reviews.