Modelio - Modelio is an open source modeling tool supporting natively UML, BPMN and model exchange with XMI.
Creately - The new interface for work to ideate, plan, and execute
Diagramo - Diagramo is an online flowchart software - diagrams (create, edit and share)
Cacoo - A cloud-based diagram maker for companies, teams, and you.
UML Designer - UML Designer provides a set of common diagrams to work with UML 2.5 models.
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.