Teampaper Snap - Take a snapshot, highlight key areas and share feedback
ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.
Epic Pen - A windows tool for drawing over your desktop and applications
Docsie - Docsie makes it easy to create and maintain your website documentation, without having to deploy it...
ppInk - a fork from gInk, with extra features (shape drawings, text,...)
ReadMe - A collaborative developer hub for your API or code.