MailScanner is an email virus scanner, vulnerability protector, and spam tagger. It supports the Postfix, Sendmail, Exim, Qmail, and ZMailer MTAs, and the Sophos, McAfee, F-Prot, F-Secure, CommandAV, InoculateIT, Inoculan, eTrust, Kaspersky, Nod32, AntiVir, BitDefender, RAV, Panda, DrWeb, ClamAV, and other anti-virus scanners. It uses SpamAssassin for highly successful spam identification, and is designed to handle denial of service attacks. It will detect password-protected zip files and apply filename checking to their contents. It is very easy to install, requires no changes at all to your sendmail.cf file, is designed to be lightweight, and won't grind your mail system to a halt with its load. It can be integrated into any email system, regardless of the software in use.
rsync is a replacement for rcp (and scp) that has many more features. It uses the "rsync algorithm" which provides a very fast method for remote files into sync. It does this by sending just the differences in the files across the link, without requiring that both sets of files are present at one of the ends of the link beforehand.
GNU grep is based on a fast lazy-state deterministic matcher (about twice as fast as stock Unix egrep) hybridized with a Boyer-Moore-Gosper search for a fixed string that eliminates impossible text from being considered by the full regexp matcher without necessarily having to look at every character. The result is typically many times faster than Unix grep or egrep.
0verkill is a client-server 2D deathmatch-like game in ASCII art. It supports free connecting/disconnecting during the game, and runs well on modem lines. Graphics are in 16-color ASCII art with elaborate hero animations. 0verkill features 4 different weapons, grenades, invisibility, and armor. The package also contains reaperbot clients, a simple graphics editor, and a level editor.
gFTP is a free multithreaded file transfer client for *NIX based machines running X11R6 or later. It has text and GTK+ 1.2/2.x interfaces and supports the FTP, FTPS (control connection only), HTTP, HTTPS, FSP, and SSH protocols and has FTP and HTTP proxy server support. It supports UNIX, EPLF, Novell, MacOS, VMS, MVS, and NT (DOS) style directory listings, and has a bookmarks menu that allows you to quickly connect to remote sites. The code is fully internationalized and there are currently 45 translations available.
Web Calendar is a powerful group calendaring and scheduling system. It is a Web based application that makes it easy to publish and manage calendar events on the internet. It includes an impressive set of features, including an easy to use interface, rich functionality, and sophisticated scheduling. It is a CGI application. It runs under your Web server, so to use it, all you need is a browser. There is no proprietary software that needs to be installed on the client side. Web Calendar runs under Unix and Windows.