draw.io - Online diagramming application
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.
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.
Pipefy - Pipefy is a process management software that empowers anyone to create and automate efficient workflows on their own without code.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Process Street - Create beautiful rich process documents in a simple to follow checklist format. Fast, free and incredibly simple to use.