Diagrammix - Tool for efficiently building attractive diagrams.
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.
Invision - Prototyping and collaboration for design teams
ProcessMaker - ProcessMaker is an easy to use BPM and workflow software solution. It is used to design, automate, and deploy business processes of any kind.
Sketch - Professional digital design for Mac.