UML Designer - UML Designer provides a set of common diagrams to work with UML 2.5 models.
StarUML - StarUML
Diagramo - Diagramo is an online flowchart software - diagrams (create, edit and share)
Visual Paradigm - Looking for an affordable software with Enterprise Architecture tool, PMBOK tool, UML tool, Agile tool, BPMN tool and UX tool? Read this page for details.
ARIS Express - ARIS Express is based on the proven ARIS methodology and industry standards.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.