Diagramo - Diagramo is an online flowchart software - diagrams (create, edit and share)
draw.io - Online diagramming application
UML Designer - UML Designer provides a set of common diagrams to work with UML 2.5 models.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
ARIS Express - ARIS Express is based on the proven ARIS methodology and industry standards.
Dot Chart - Dot Chart is simple and quick online process mapping system.