Creately is a web based diagramming tool with real-time collaboration to work together on diagrams. If you're not comfortable storing data on the cloud you can use the desktop version. It lets you create workflows, mind maps, concept maps, business process models, wire-frames, org charts and many more diagram types useful in research projects.

Gliffy is a tool that makes it easy to create, share, and collaborate on a wide range of diagrams. Gliffy works directly in your browser and can be used to build flow charts, organization charts, network diagrams, workflows, technical drawings, and wireframes.

Instaviz is a pocket whiteboard for the iPhone, iPad or iPod Touch. You sketch rough shapes and lines, and Instaviz transforms them into laid-out diagrams.

Text 2 Mind Map is a web-based tool for mind mapping. Very basic interface and functionality. Requires users to structure information in a linear text outline, which it returns as a diagram.