Typorama - Typorama: Text on Photo Editor is a Typography Art and Poster Maker application created and published by Apperto Ltd.
SocialSizes - Sketch templates for sharing images & videos on social media
Facebook Creative Hub - A new way to create & preview mockups for ads with Facebook
Social Templates Bundle for Instagram - Large bundle of 240 posts & stories templates for Instagram
Enhance - Find, crop, edit, & share pics to social. Made by Hootsuite.
Video Templates By VEED.IO - Professional & editable online video templates for social