OpenCanvas
OpenCanvas is a popular computer graphics software program created by Portalgraphics. It was specifically designed for use with pressure-sensitive drawing tablets; it is a sketch program rather than a general-purpose graphic design program.
Its popular for being fast and lightwieght, while still being powerful enough for many works. the paintchat feature can be used for graphical Collaboration, as well as simple rapid Ideation
It was originally released as freeware, but the authors moved to a demo/retail model starting with version 2. openCancas 1.1 b72, the last free version, is available to download.
