Imixs-Workflow - Imixs Workflow is a BPM Framework with the goal to reduce the complexity of business applications.
draw.io - Online diagramming application
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.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Kissflow - Kissflow is a workflow tool & business process workflow management software to automate your workflow process. Rated #1 cloud workflow software in Google Apps Marketplace.
Dot Chart - Dot Chart is simple and quick online process mapping system.