flex.rb is a regexp matching and scanning library for the Ruby language. It is more than 3 times faster than Ruby regexps, and supports matching text arriving in multiple parts (via async, non-blocking I/O). flex.rb embeds the GNU Flex 2.5.4 (fast lexical analyzer generator) as an engine, and all of Flex's functionality is accessible from Ruby scripts.
quote.rb is a Ruby script which defines more than 70 quoters (basic string manipulation routines). Most quoters just add or remove backslashes at the appropriate place; others include hexdumps, checksums, simple encryptions, etc. quote.rb's main goal is to provide all quoters necessary for simple and advanced web programming (CGI and server-side scripting) in one place.
QuantLib is a cross-platform, quantitative finance C++ library for modeling, pricing, trading, and risk management in real-life. It is also wrapped as Python/Ruby/Scheme modules. Extensions for Excel, R, and Mathematica are available. Other such extensions are under consideration. QuantLib offers tools that are useful both for practical implementation and for advanced modeling. It features market conventions, yield curve models, solvers, PDEs, Monte Carlo (low-discrepancy included), exotic options, VAR, and so on.
Csv2vcard is a program for converting CSV (comma separated values, as exported by software such as MS Outlook) files containing contact information to the industry standard vcard format, which can be imported by most mailers and PIM software (optimized for Evolution). It's based on a Perl script by Michael MacDonald of Ximian. Csv2vcard can be used to convert any CSV format, not just the English Outlook output.
RDQS (Ruby Data Query Shell) is a text-based shell for querying SQL databases. It features connection bookmarks, shortcuts, history, completion, paging, shell interaction (via backtick operator), CSV/INI/XML/Table output, output redirection, numerous configuration options, multiconnect with fast switching, and a watch command (execute given query/shortcut in a fixed interval).