I've been fiddling with these libraries the last couple of days.
- Text: Useful text utility library. Includes Soundex, Metaphone, Figlet, Metaphone, and Levenshtein distance.
- RMovie: FFmpeg library wrapper. It's a real pain in the ass to install, but once you get it working, it allows you to extract arbitrary frames from any video format supported by FFmpeg.
- Hpricot: HTML scraper. Similar to Rubyful Soup, but much faster and with partial support for both CSS selectors and XPath.
They're all avaiable as Ruby Gems, too.