Developed by the Free Software Foundation and UNESCO, this directory lists free software that runs under free operating systems. Over 4,000 software packages are listed by subject; it is also fully searchable.
GitHub is a service to help software developers. It uses Git for revision control and source code management. GitHub offers 2 plans: a paid plan for private projects and a a free plan for open source projects. There are also social networking aspects including feeds and following that allows developers to collaborate.
A metasite containing freely available software, conference proceedings, and databases of interest to the numerical and scientific computing communities.
The OpenScience Project contains a directory of open source scientific software. The computer science section lists resources under several categories including: algorithms and computational theory; artificial intelligence; data communication; human-computer interaction; languages; measurement and evaluation; simulation and modeling; software engineering; and symbolic and algebraic manipulation. A search engine is also included.
The heart of this site is the Perl Guide, a listing of nearly 4,000 Perl CGI programs. The guide is divided into dozens of categories. Each listing contains the program name, operating system, a description, and cost.