Sanewall is a firewall builder for Linux that uses an elegant language abstracted to just the right level. This makes it powerful and easy to use, audit, and understand. It allows you to create very readable configurations even for complex stateful firewalls. Sanewall can be used for almost any purpose, including control of any number of internal/external/virtual interfaces, control of any combination of routed traffic, setting up DMZ routers and servers, all kinds of NAT, providing strong protection (flooding, spoofing, etc.), transparent caches, source MAC verification, blacklists, and whitelists. Newer versions abstract the differences between IPv4 and IPv6, allowing you to define a common set of rules for both, while permitting specific rules for each as you need. Sanewall is a fork of FireHOL and can make use of existing FireHOL configurations.
conntrack-tools is a set of userspace tools for Linux that allow system administrators to interact with the Connection Tracking System, the module which provides stateful packet inspection for iptables. It includes the userspace daemon conntrackd and the commandline interface conntrack.
The GNOME NetworkManager is a set of co-operative tools that make networking simple and straightforward. Whether wireless or wired, NetworkManager allows you to quickly move from one network to another: once a network has been configured and joined once, it can be detected and re-joined automatically at a later date. It was designed to auto-detect as much information as possible, seamlessly switches connections when necessary, and provides immediate feedback of the network state to users and applications.
XRoar is a cross-platform emulator for the Dragon 32, Dragon 64, and Tandy CoCo computers, all originally released in the early '80s. The emulator runs under Unix-like operating systems (including Mac OS X) and Windows, with older versions available for handhelds like the Nintendo DS and GP32.
Flac2All is a multi-threaded script that will convert your collection of FLAC files into either Ogg Vorbis, MP3 (with the Lame encoder), or FLAC, complete with any tags and identical file/folder structure. The script has been stable for about a year now, and it has been known to saturate 8-core machines with parallel conversions. It is useful for people with with large FLAC collections who also want a lossy version for portable media players. If wanted, the script can perform updates by skipping already converted files. It has only been tested on Linux, but it should work without alteration on the other Unix systems with bash and the required dependencies.
Kst is a fast real-time large-dataset viewing and plotting tool with built-in data analysis functionality. It contains many powerful built-in features and is expandable with plugins and extensions. It features powerful keyboard and mouse plot manipulation, a large selection of built-in plotting and data manipulation functions (such as histograms, equations, and power spectra), built-in filtering and curve fitting capabilities, a convenient command-line interface, a powerful graphical user interface with non-modal dialogs for an optimized workflow, support for several popular data formats, extended annotation objects similar to vector graphics applications, and high-quality export to bitmap or vector formats,