I am using Gliffy a lot. It is a great graphic tool (free Chrome extension) to create flowcharts, UML diagrams, network diagrams and much more. Very important is the rubber-banding support: when you connect objects using their red indicated connections (during drawing), these connections are maintained wherever you drag the objects.
https://chrome.google.com/webstore/detail/gliffy-diagrams/bhmicilclplefnflapjmnngmkkkkpfad