Seashore is an open source image editor for Mac OS X's Cocoa framework. It features gradients, textures and anti-aliasing for both text and brush strokes. It supports multiple layers and alpha channel editing. It is based around the GIMP's technology and uses the same native file format.
Gephi is an interactive visualization and exploration platform for all kinds of networks and complex systems, dynamic and hierarchical graphs. Runs on Windows, Linux and Mac OS X. Gephi is open-source and free.
Agna is a freeware application designed for social network analysis, sociometry and sequential analysis. Platform-independent, friendly and easy-to-learn, integrated visual network editor, html output, free.
TG-Gallium3D is a hardware- and API- neutral intermediate format that will allow Tungsten Graphics to efficiently build graphics drivers to support a variety of hardware platforms for modern 3D APIs on various OS environments.
The Rasterbator creates huge, rasterized images from any picture. Upload an image, print the resulting multi-page pdf file and assemble the pages into extremely cool looking poster up to 20 meters in size.
With DrawBerry, you have all the possibilities the vectorial drawing offers you in a free, easy to use and powerful application. If you don't need applications such Illustrator or Inkscape and you want to create some simple (or less simple) illustrations, DrawBerry is for you.