Kindle Fire Stand
I made this stand for my Kindle Fire. It would probably hold other tablets quite nicely but I've only tested it with the Fire. Works horizontally and vertically.
Print two of each part and snap the cross pieces into the vertical supports. Make sure you push each cross piece out to it's stop. They will likely be tight fit but each slot is a little deeper than it needs to be which should allow the plastic to flex. I've printed it in PLA and it snapped together quite tightly. If it seems loose you may elect to put a spot of glue on each joint, if it seems too tight push harder.