draw.io
draw.io is completely free online diagram editor built around Google Drive(TM), that enables you to create flowcharts, UML, entity relation, network diagrams, mockups and more. Your data is stored only in Google Drive, so no additional third-party to trust with your data. draw.io can import from .vsdx, .vsd, Gliffy(TM) and Lucidchart(TM) files.
