At Cacoo, you can create diagrams in real time collaboration.
Cacoo is a user friendly online drawing tool that allows you to create a variety of diagrams such as site maps, wire frames, UML and network charts. Cacoo can be used free of charge.
You can no doubt see by my illustrated sample that I have little need of Cacoo's service. I automatically tried to tell a story, which is not what it's about. But it's an impressive tool for those who need to create diagrams. There is a nice range of shapes and stencils you can use, plus customize to colour and fit your page. Dragging those to place, then connecting them, takes mere moments. Another feature I liked is that it really does allow for realtime collaboration, so you can work together with someone else on your flowchart, say.
There's a video you can watch to understand it better, and I've embedded it below. Another new diagram-making program is Simple Diagrams which I read about recently at Free Technology for Teachers. It is a download, but looks to be exactly what it says. There's a free and paid version.
Cacoo - Real-time Collaborative Diagramming & Design from Nulab Inc. on Vimeo.