distributed.net is a loosely knit group of computer users from all of the world that is taking up challenges requiring lots of computing power (most notably the RC5, DES, and OGR cracking contests). It is simple to participate in the challenges by downloading and running their client software (which uses idle CPU time to complete its tasks).
Cfengine is a tool for setting up and maintaining BSD and System-5-like operating system optionally attached to a TCP/IP network. You can think of cfengine as a very high level language, much higher level than Perl or shell: a single statement can result in many hundreds of operations being performed on multiple hosts. Cfengine is good at performing a lot of common system administration tasks, and allows you to build on its strengths with your own scripts.
Terraform allows you to create fractal terrain (also called a height field) and transform it using a number of algorithms. It is meant to be a tool for those who want to generate digital terrain models for use in raytracing or other simulations. Terraform features different views and colormaps and has a preview mode which features interactive real-time rotation of the terrain object. Terraform is written for the GNOME desktop environment.
DNRD is a proxy DNS daemon. It supports several forward servers for redundancy and/or load-balancing. DNS queries for specific domains can be forwarded to a specific group of DNS servers (with redundancy and load balancing) for that domain. It is very useful in VPN and dialup environments but can also be used as a DNS cache or ad-blocker for networks and workstations.