BitTorrent is a tool for copying files from one machine to another. FTP punishes sites for being popular. Since all uploading is done from one place, a popular site needs big iron and big bandwidth. With BitTorrent, clients automatically mirror files they download, making the publisher's burden almost nothing.
BRL-CAD is a powerful constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing support for rendering and geometric analysis, path-tracing for realistic image synthesis, network distributed framebuffer support, and image and signal-processing tools.
Steel Bank Common Lisp is a development environment for Common Lisp, with excellent support for the ANSI standard: garbage collection, lexical closures, powerful macros, strong dynamic typing, incremental compilation, and the famous Common Lisp Object System (multimethods and all). It also includes many extensions, such as native threads, socket support, a statistical profiler, programmable streams, and more. These are all available through an integrated, interactive native compiler which feels like an interpreter. SBCL is unique in being a multiplatform native compiler which bootstraps itself completely from source, using a C compiler and any other ANSI Common Lisp implementation.
Moosic is a music player that focuses on easy playlist management. It consists of a server process that maintains a queue of music files to play and a client program which sends commands to the server. The server continually runs through its playlist, popping items off the top of the list and playing each with an external program. The client is a simple command-line utility which allows you to perform powerful operations upon the server's queue, including the addition of whole directory trees, automatic shuffling, and item removal according to regular expressions. The server comes configured to play MP3, Ogg, MIDI, MOD, and WAV files.
Java Development Environment for Emacs (JDEE) is an Emacs-based integrated development environment (IDE) for developing Java applications and applets. Features include multiple code browsers, a JPDA-based debugger, method and field completion, template-based and procedure-based code generation, Java source code interpreter, context-sensitive help, and more.
The National Space Science Data Center's (NSSDC) Common Data Format (CDF) is a self-describing data abstraction for the storage and manipulation of multidimensional data in a platform- and discipline-independent fashion. It consists of a scientific data management package (known as the "CDF Library") that allows programmers and application developers to manage and manipulate scalar, vector, and multi-dimensional data arrays.
Werc is a minimalistic RESTful Web application framework and content management system. It follows the Unix "tool philosophy" and it is designed to be fast, simple, convenient, and easily extensible. It handles both small and big sites and has a flexible system for user and group permissions. All data is stored in plain text files that can be easily manipulated with standard tools, without using any databases or other external dependencies. Existing applications include a blogging engine with RSS/Atom feeds, a wiki system that can easily integrate pre-existing documents (can be enabled for any directory tree), and others.