TaskBoard - A Kanban-inspired app for keeping track of things that need to get done.
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
LeanKit by Planview - See how Planview LeanKit enables engineering teams across all levels of the organization with a visual work delivery tool to apply Lean management principles to their work, helping them work smarter and deliver faster.
draw.io - Online diagramming application
buckets.co - Feature rich kanban board collaboration platform.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.