SOGo is a very fast and scalable modern collaboration suite (or groupware). It offers calendaring, address book management, and a full-featured Webmail client along with resource sharing and permission handling. It also makes use of documented standards (IMAP, CalDAV, CardDAV, etc.) and thereby provides native connectivity (without plugins) to many clients such as Microsoft Outlook, Apple iCal, the iPhone, Mozilla Lightning, and a plethora of mobile devices via SyncML. It can reuse any existing email and database infrastructure, avoiding long hours of site restructuring.
distcc is a parallel build system that distributes compilation of C/C++/ObjC code across machines on a network. It can be set up in just a few minutes and makes builds up to ten times faster. It does not require machines to share a filesystem or have the same libraries or header files, and installation does not need superuser privileges.
GPP is a general-purpose preprocessor with customizable syntax, suitable for a wide range of preprocessing tasks. Its independence from any programming language makes it much more versatile than cpp, while its syntax is lighter and more flexible than that of m4. The syntax is fully customizable, which makes it possible to process text files, HTML, or source code equally efficiently in a variety of languages.
Fugu SSH is a Mac OS X graphical frontend to OpenSSH's Secure File Transfer application (SFTP). SFTP is similar to FTP, but, unlike FTP, the entire session is encrypted, meaning no passwords are sent in cleartext form, and it is thus much less vulnerable to third-party interception. Fugu allows you to take advantage of SFTP's security without having to sacrifice the ease of use found in a GUI. Fugu also includes support for SCP files transfers, and the ability to create secure tunnels through SSH.
GNUSTEP Live CD contains a lot of software for GNUstep, a free implementation of the OPENSTEP framework (which is also directly used in Mac OS X as Cocoa). It includes excellent applications for RAD (GORM and ProjectCenter). The CD is available for i486, AMD64, Apple Mac PowerPC, and Sun UltraSPARC computers.