GKrellM is a GTK-based stacked monitor program that charts SMP CPUs, disks, load, active net interfaces, and internet connections. There are also builtin monitors for memory and swap, file systems with mount/umount feature, mailbox checking including POP3 and IMAP, clock/calendar, laptop battery, sensors (temperatures, voltages, and fans), and uptime. It has LEDs for the net monitors and an on/off button and online timer for PPP. There is a GUI popup for configuration, plugin extensions can be installed, and many themes are available. It also features a client/server monitoring capability.
Ettercap is a network sniffer/interceptor/logger for ethernet LANs. It supports active and passive dissection of many protocols (even ciphered ones, like SSH and HTTPS). Data injection in an established connection and filtering on the fly is also possible, keeping the connection synchronized. Many sniffing modes were implemented to give you a powerful and complete sniffing suite. Plugins are supported. It has the ability to check whether you are in a switched LAN or not, and to use OS fingerprints (active or passive) to let you know the geometry of the LAN.
OpenVPN is a robust and highly configurable VPN (Virtual Private Network) daemon which can be used to securely link two or more private networks using an encrypted tunnel over the Internet. OpenVPN's principal strengths include wide cross-platform portability, excellent stability, support for dynamic IP addresses and NAT, adaptive link compression, single TCP/UDP port usage, a modular design that offloads most crypto tasks to the OpenSSL library, and relatively easy installation that in most cases doesn't require a special kernel module.
MP-MICH is a Multi-platform uniform MPI implementation, based on MPICH and SCI-MPICH, resulting in a high performance, consistent MPI across both ethernet and SCI networks in a hybrid environment. There is a single, standardized source tree for all platforms. It is compliant with the MPI-1 standard.
GNU VPE creates a virtual ethernet by creating host-to-host tunnels between multiple endpoints. Unlike other virtual private "network" solutions which merely create a single tunnel, it creates a real network with multiple endpoints. It is designed to be conceptually simple and straightforward to setup (assuming prior IP routing knowledge) without sacrificing flexibility. It is designed to sit on the gateway machines of company branches to connect them, but it can also be used to tunnel into a VPN with a variety of protocols (RAW IP, ICMP, UDP, TCP, HTTPS-Proxy, DNS).
netscript is a portable/multi-platform, lightweight TCP/UDP socket scripting system. It is intended to automate situations, built on a word-to-word ruleset response system. It includes wildcard support, character replacement, random replacement, argument inclusion, server timeout, initial send, display altering, multiple character dump formats, telnet protocol support, logging, program to socket dumping, executable ruleset support, reverse binding, module support, data truncation, data formatting, permission options, virtual hosting support, history storage, dynamic storage variables, directory placement, character omitting, timed rules, background support, syslog support, routing support, socket options, interactive mode, and graphical user interface support.