Xcerpt is a declarative, rule-based query and transformation language for XML, inspired by logic programming. Instead of the path-based navigational approach taken by languages like XSLT and XQuery, Xcerpt uses pattern-based, positional queries, where a pattern is an "example" of the database containing variables for binding content. As in logic programming, rules may be chained to form more complex queries.
twidge is a client for microblogging sites such as Twitter and Identica (identi.ca). It is extremely versatile, can be customized to work the way you want to work, and can be combined with other tools to do just about anything. It can be used interactively from the shell. It is useful directly as-is, and with simple shell aliases can make a highly efficient system to do exactly what you want. It is perfectly capable of being your only client for microblogging. It can also be used in an automated way, via cron(1), or it can even integrate with your email system.
Hoplax is a power user tool to store bookmarks in text files and manage them efficiently. Bookmarks stored in Hoplax are easy to edit and search with normal Unix tools and editors. They are easy to synchronize with git/svn/darcs/etc. Bookmarks can be categorized easily into files, and you can choose to not synchronize a file to a computer, e.g. confidential company bookmarks to home computers. The filtering is smarter than the browser's location bar. Keyword bookmarks with multiple parameters and auto-completion are supported.