GitHub is a distributed version control system for the collaborative development of software. Public repositories are free and unlimited. Various pricing plans are available for private repositories.
Google Code Project hosting is a free collaborative development environment for open source projects. Each project comes with its own member controls, Subversion/Mercurial/Git repository, issue tracker, wiki pages, and downloads section.
Cinder is a C++ library for programming with aesthetic intent - the sort of development often called creative coding. This includes domains like graphics, audio, video, and computational geometry. Cinder is cross-platform, with official support for OS X, Windows, iOS, and WinRT.
Greenhouse is a creative coding toolkit for spatial interfaces. Greenhouse enables creative coders and engineers to rapidly prototype spatial interfaces: multi-screen, multi-user, multi-device interfaces leveraging gestural and spatial interaction. Working knowledge of C++ and OpenGL is recommended but not required. Greenhouse is available now for Mac OS X and Linux (soon) and is free for non-commercial use.
Music21 is a set of tools for helping scholars and other active listeners answer questions about music quickly and simply. If you’ve ever asked yourself a question like, “I wonder how often Bach does that” or “I wish I knew which band was the first to use these chords in this order,” or “I’ll bet we’d know more about Renaissance counterpoint (or Indian ragas or post-tonal pitch structures or the form of minuets) if I could write a program to automatically write more of them,” then music21 can help you with your work.
openFrameworks is an open source C++ toolkit designed to assist the creative process by providing a simple and intuitive framework for experimentation. openFrameworks is designed to work as a general purpose glue, and wraps together several commonly used libraries. The code is written to be massively cross-compatible. Right now we support five operating systems (Windows, OSX, Linux, iOS, Android) and four IDEs (XCode, Code::Blocks, and Visual Studio and Eclipse). The API is designed to be minimal and easy to grasp.