Programming Interactivity: 2nd Edition
The 2nd Edition of one of my favorite books is out, Programming Interactivity, from the incredible Joshua Noble. More info:

Syphon Introduction from vade on Vimeo.
Syphon is an open source Mac OS X technology that allows applications to share frames - full frame rate video or stills - with one another in realtime. Now you can leverage the expressive power of a plethora of tools to mix, mash, edit, sample, texture-map, synthesize, and present your imagery using the best tool for each part of the job. Syphon gives you flexibility to break out of single-app solutions and mix creative applications to suit your needs.
Syphon provides an ecosystem for sharing imagery between applications and new media development environments. Syphon is designed to be efficient and will not duplicate resources unnecessarily, keeping your frame rate and best interests in mind.
Syphon > Unity port by Brian Chaslow and Vade.
Via: @briangibson
Via: @memotv
Via: @REAS
Structure Synth is a cross-platform application for generating 3D structures by specifying a design grammar. Even simple systems may generate surprising and complex structures. The design grammar approach was originally devised by Chris Coyne (for a 2D implementation see the popular Context Free Art).
Features:
Structure Synth is built in C++, OpenGL, and Qt 4. Builds are currently provided for Windows and Mac. It is possible to compile Structure Synth on Linux as well. On Debian and Ubuntu a 'structure-synth' package exists.
The progress and design considerations can be tracked at the Syntopia blog.
Soft Lighting by Mikael Hvidtfeldt Christensen (Syntopia)
Fragmentarium is an open source, cross-platform IDE for exploring pixel based graphics on the GPU.
It is inspired by Adobe's Pixel Bender, but uses GLSL, and is created specifically with fractals and generative systems in mind.
Features:
Fragmentarium is built in C++, OpenGL/GLSL, and Qt 4.
Fragmentarium is currently in the early development phase, but is getting more mature! Read more about getting Fragmentarium or more about using Fragmentarium.
Via: Eskil Steenberg