The atheist Blog Roll relies entirely on free technologies; the only costs are related to hardware and internet connectivity.  We are using the following:

NetBSD 5
http://www.netbsd.org/

The Operating System we use is NetBSD running on Intel and Seagate hardware.  NetBSD is a free, open-source, high quality, standards compliant, commercial-grade Operating System that provides an efficient and reliable Unix-like environment which is ideally suited to internet site hosting (among many other things).

Apache HTTPd 2.2
http://httpd.apache.org/

The web server software we use is Apache's HTTPd server.  Apache HTTPd is the free, open-source web server daemon of choice and is used in all types of environments meeting the needs of people ranging from part-time hobbyists to departments and customers of international multi-billion dollar corporations.  Although many commercial web server products are available in the marketplace, Apache HTTPd is the de facto standard solution due to its vast feature-set, highly-flexible configuration, quality documentation, and compliance with official internet standards.  We also like it because it's efficient and reliable.

Perl 5
http://www.perl.org/

All our back-end web programming is in the internationally acclaimed Perl language.  Perl is an intensely flexible language that has many similarities in its development path to that of a "natural language" [such as English or Chinese], in both its written and spoken forms.  Perl is one of the most advanced programming languages of all time and was at the pioneering heart of CGI development which all interactive web sites depend on today to facilitate connectionless client/server communications (ranging from the roots in simple HTML form handling, to dynamic content utilizing AJAX for real-time updates driven by client-side JavaScript code and/or Java applets).

Perl is a very well-supported language, which continues to gain new interest today despite radical claims that it is a dying language -- it has kept pace, after all, with current technologies, but without abandoning older technologies that are still in use today (it is Perl's inherent flexibility, and community interest, that has made this possible).  Perl is such a significant language that there is a dedicated IRC network with multiple servers world-wide located on different continents, which is available at http://irc.perl.org/.

ModPerl 2
http://perl.apache.org/

We utilize mod_perl2 with APR (http://apr.apache.org/), which integrates directly into Apache HTTPd server.  In addition to the well-known performance gains, mod_perl2 also provides direct access to a wide range of internal web server functions at both the programming and configuration stages.

If you'd like to know more about creating web sites with ModPerl, the www.ModPerl.pl web site includes a helpful step-by-step guide that simplifies installation and configuration, and includes working source code examples that will get you started quickly.

PostgreSQL Server
http://www.postgresql.org/

PostgreSQL is the reliable, high-performance, mission-critical-capable, standards-compliant, fully transactional SQL server software that we use in the back-end for all our database needs.  This is a robust product with a helpful, knowledgeable, and friendly support community that benefits from contributors in most countries, many of whom are also known to be using PostgreSQL professionally in their work.

Midnight Commander
http://www.midnight-commander.org/

Midnight Commander is a feature-rich full-screen visual text-mode file manager application that makes it easy for users to efficiently copy, move, and delete files and whole directory trees, search for files, and run commands in the subshell, all with internal viewer and editor functions included.

Based on the famous Norton Commander for DOS and perhaps also its successor, the FAR Manager which is a native MS-Windows text-mode application, the Midnight Commander is the continuation of this versatile style of file management applications on Unix and Unix-like Operating Systems.

Others will be added in the near future...