xMarkup is a command line and GUI utility for multipurpose processing of a set of text files. It can be used to generate or edit the navigational cross-references within a set of HTML documents, analyze and convert the structure or content of SGML, XML, HTML, or text documents, split or merge text files with specified rules, analyze and extract data, generate scripts, and more. xMarkup supports a built-in procedural language which may be used to describe rules of the processing. This language is a simple dialect of the Icon programming language.
xRecurseDiff is a small program that can rapidly traverse entire directory trees to show the differences between different copies of the same file. It can be useful for code analysis, expecially for collaborative development. For example, it can analyze differences before a CVS/SVN submission or to resolve a conflict in concurrent editing.
xSH-Paranoia Patch is an project started for admins who work in large system environments. It allows you to see which user executes which command, when, where, and from what IP address. It logs everything to syslog, and with syslog-ng, you can log it to another machine where no user should/would have access. Currently supported shells are bash and tcsh.
xSiteable is a complete all-you-need package for creating sites that are fully relational, open source, fully templating-enabled, using only XML-based technologies to help you create complex sites on the fly. It packs such features as topic maps, notation for content, and the fast Sablotron xslt parser.
XAD is a Linux-PAM module which allows a system administrator to control authentication in a very fine-grained manner. This module is very easy to configure, and allows access to be controlled on the basis of many properties of the system or the user who is trying to authenticate.