Modelio - Modelio is an open source modeling tool supporting natively UML, BPMN and model exchange with XMI.
Kalam Labs - Twitch for Science
Diagramo - Diagramo is an online flowchart software - diagrams (create, edit and share)
RunaWFE - RunaWFE Free is a free Open Source BPMS (business process management system), which serves to optimize and automate business processes (for Windows, Linux, Mac OS).
UML Designer - UML Designer provides a set of common diagrams to work with UML 2.5 models.
Litnerd - The Pixar for education, reading program for K-5 schools