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.
glark offers grep-like searching of text files, with very powerful, complex regular expressions (e.g., "/foo\w+/ and /bar[^\d]*baz$/ within 4 lines of each other"). It also highlights the matches, displays context (preceding and succeeding lines), does case-insensitive matches, and automatic exclusion of non-text files. It supports most options from the GNU version of grep.
regexp-engine is a regexp engine written entirely in Ruby that makes it possible to search in text with advanced search patterns. It supports Perl 5 and some Perl 6 syntax and is fairly compatible with Ruby's native regexp engine, passing almost 98% of the Rubicon tests. The implementation is simple and contains no optimizations.
deplate converts wiki-like markup to LaTeX (standard classes, koma, dramatist, sweave), HTML/PHP (single page, chunked/website, HTML, or s5-based slideshow), DocBook (article, book, man/ref page), and really plain text. Currently supported input formats are viki and Ruby's rdoc. The viki markup supports footnotes, citations, index, table of contents, embedded LaTeX for mathematics, integration with R for dynamically generated figures and tables, and more. Output can be customized via page templates.
SiSU (Structured information, Serialized Units) is a lightweight markup based, text structuring and publishing framework (that features granular search). With minimal markup of a plaintext file, it produces: plain-text, HTML, XHTML, XML, ODF, LaTeX, PDF, and populates an SQL database at an object/paragraph level for granular searches. Prepare documents using your text editor of choice, then use SiSU to generate the desired output formats. SiSU is controlled from the command line.