Fukuoka-based nulab, Inc. [ja] launched a real-time collaboration tool for drawing diagrams called Cacoo.
With its real-time synchronization technology, you can edit files on Cacoo while other team member is working on it. The pre-defined stencil sets include parts for network diagrams, sitemaps, wireframes, and UMLs, in addition to generic shapes and illustrations.
Cacoo is proposing another solution for the problem MockFlow and Gliffy has been addressing for a while — an easy visual communication tool for remote project members. Combining the real-timeness of MockFlow and versatility of Gliffy along with extra features (e.g. automatically updating exported images after additional changes are made), they may be able to show what’s been missing for wider user adoption of tools in that arena.
Cacoo is free for all users at the moment. They are planning to introduce a “premium” plan in 2010.