Diagrammix - Tool for efficiently building attractive diagrams.
Modelio - Modelio is an open source modeling tool supporting natively UML, BPMN and model exchange with XMI.
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.
Diagramo - Diagramo is an online flowchart software - diagrams (create, edit and share)
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.
UML Designer - UML Designer provides a set of common diagrams to work with UML 2.5 models.