CoSketch - CoSketch is a multi-user online whiteboard designed to give you the ability to quickly visualize and share your ideas as images. No registration or plugins required.
ApproveIt for Slack - Get approvals in minutes, not days. Right from Slack!
Conceptboard - Instant Whiteboards for Teams & Projects
AccessOwl - Discover Shadow IT, Automate Access Reviews and Auto-Provisioning — No Enterprise-Subscriptions required.
Twiddla - Mark up websites, graphics, and photos, or start brainstorming on a blank canvas.
Approve app for Zendesk - Any enforceable and auditable approval workflow for Zendesk tickets you can imagine can be easily created using the Approve app.