Modelio - Modelio is an open source modeling tool supporting natively UML, BPMN and model exchange with XMI.
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.
Diagramo - Diagramo is an online flowchart software - diagrams (create, edit and share)
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
UML Designer - UML Designer provides a set of common diagrams to work with UML 2.5 models.
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project