Just watched Railscast Episode 190 in which Ryan Bates demonstrated the use of the Nokogiri Gem for a screen scraping application. As part of the episode, Ryan also demonstrated the use of SelectorGadget, a browser bookmarklet for exploring CSS styles on a page which is useful in Nokogiri for identifying CSS selectors to use to grab a particular HTML element (or group of elements). I had seen SelectorGadget recommended as a learning tool for jQuery as well, and Ryan's screencast was a useful reminder.</p>

Incidently, Nokogiri is used by the Rspec and Cucumber testing tools for Rails view testing.