Synergy - Cross-platform software for sharing your mouse and keyboard between multiple computers
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.
Input Director - Control multiple windows systems with one keyboard/mouse. Share a keyboard and mouse across multiple windows system.
draw.io - Online diagramming application
Barrier - Barrier is a cross-platform software for sharing your mouse and keyboard between multiple computers...
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.