Camunda - The Universal Process Orchestrator
asciiflow - Infinite ASCII diagrams, save to Google Drive, resize, freeform draw, and export straight to text/html.
jBPM - jBPM is a flexible Business Process Management (BPM) Suite.
Core2D - A multi-platform data driven 2D diagram editor.
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.
PathVisio - Open-source and free pathway analysis and pathway drawing software. Allows drawing, editing and analysis of biological pathways.