ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.
Teampaper Snap - Take a snapshot, highlight key areas and share feedback
Docsie - Docsie makes it easy to create and maintain your website documentation, without having to deploy it...
Epic Pen - A windows tool for drawing over your desktop and applications
ReadMe - A collaborative developer hub for your API or code.
Pylote - To draw on the screen and to handle the instruments of geometry there.