CTSim is a Computed Tomography simulator. It simulates the process of obtaining x-ray data around a phantom object. It then uses various reconstruction algorithms for reconstructing the original image. It supports animation of projection and reconstruction processes, 3-dimensional viewing using OpenGL as well as cross platform support using GTK and Win32.
DansGuardian is a Web content filtering proxy that uses Squid to do all the fetching. It filters using multiple methods including, but not limited to, phrase matching, file extension matching, MIME type matching, PICS filtering, and URL/domain blocking. It has the ability to switch off filtering by certain criteria including username, domain name, source IP, etc. The configurable logging produces a log in an easy to read format. It has the option to only log text-based pages, thus significantly reducing redundant information (such as every image on a page).
DarkIce is a live audio streamer. It records audio from an audio interface (e.g. a sound card), encodes it, and sends it to a streaming server. DarkIce can record from OSS audio devices, ALSA audio devices, Solaris audio interfaces, and Jack sources. DarkIce can encode into MP3, MP2, Ogg Vorbis, and AAC formats, and can send the encoded stream to ShoutCast, IceCast 1.3.x and 2.x, and the Darwin Streaming Server.
dhcpcd is an RFC2131 compliant DHCP client. It is fully featured and yet lightweight: the binary is 60k as reported by size(1) on Linux i386. It has support for duplicate address detection, IPv4LL, carrier detection, and a merged resolv.conf and ntp.conf for which other DHCP clients require third party tools.
dircproxy is an IRC proxy server ("bouncer") designed for people who use IRC from lots of different workstations or clients, but wish to remain connected and see what they missed while they were away. You connect to IRC through dircproxy, and it keeps you connected to the server, even after you detach your client from it. While you're detached, it logs channel and private messages as well as important events, and when you reattach it'll download those logs to you using ordinary IRC protocol.
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).