2. Mail GpgGPG/MIME extension for the Ruby Mail Library
4. RdigCrawler and content extractor for building a full text index of a website's contents. Uses Ferret for indexing.
5. Pdf FormsFill out PDF forms with pdftk (http://www.accesspdf.com/pdftk/).
7. ferretFerret: the extensible information retrieval library for ruby.