Diagramo - Diagramo is an online flowchart software - diagrams (create, edit and share)
draw.io - Online diagramming application
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.
ARIS Express - ARIS Express is based on the proven ARIS methodology and industry standards.
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.