EtherApe is a GNOME/pcap-based etherman, interman, and "tcpman" clone. It displays network activity graphically. Active hosts are shown as circles of varying size, and traffic among them is shown as lines of varying width. It supports Ethernet, FDDI, Token Ring, ISDN, PPP, WLAN, and SLIP transports. It knows about VLANs, IP, IPv6, TCP, UDP, FTP, and a number of other protocols. Additional statistics windows will let you concentrate on protocols or nodes.
The OpenCA Project is a collaborative effort to develop a robust, full-featured and Open Source out-of-the-box Certification Authority implementing the most used protocols with full-strength cryptography world-wide. OpenCA is based on many Open-Source Projects. Among the supported software is OpenLDAP, OpenSSL, Apache Project, Apache mod_ssl.
ZABBIX is an enterprise-class distributed monitoring solution designed to monitor and track performance and availability of network servers, devices, and other IT resources. It supports distributed and Web-based monitoring, auto-discovery, real-time monitoring, SLA assurance, trending, and more.
retawq is a multi-threaded Web browser for text terminals on computers with Unix-like operating systems. It is fast, small, nicely configurable, and comfortable; e.g. the low-level network communications are performed in a non-blocking way, and you can keep open as many "virtual windows" as you want and work simultaneously in two of them in a split-screen mode.
di is a disk information utility that displays everything that df does and more. It features the ability to display your disk usage in whatever format you prefer. It also checks the user and group quotas, so that the user sees the space available for their use, not the system wide disk space. It is designed to be highly portable across many platforms and is great for heterogenous networks.
Drivel is a GNOME client for working with online journals, also known as weblogs or simply blogs. It retains a simple and elegant design while providing many powerful features, including support for LiveJournal, Blogger, MovableType, Advogato, and Atom journals. (Systems based off these are also supported, including WordPress and Drupal.)
LiVES is a simple to use yet powerful video effects, editing, conversion, and playback system aimed at the digital video artist and VJ. It runs under Linux, BSD, Mac OS X/Darwin, IRIX, and openMosix. It is frame and sample accurate, can handle almost all types of video, and is fully extendable through plugins and the included plugin builder tool. It can also be controlled remotely using OSC.