Weava - Workspace to highlight, organize & collaborate on your research articles.
ScreenTray - A better way to capture, annotate and share screenshots
Good Annotations - A online annotation tool that is perfect for providing feedback to your team.
Genius Annotations - Embed text annotations on your site. Annotate the web.
Marker.io for Slack - Turn screenshots into Slack messages ✌️
Annotate by Convergely - Easily annotate images you get on Slack - just like Skitch