MonkeySupport: Boosting Rails With Patches of C
As you probably know, it's possible to use C to write Ruby extensions and even to use C inline with Ruby if you have RubyInline installed. MonkeySupport uses Ruby's C integration provisions to provide super-fast C equivalents of Rails' ActiveSupport library.
Burke advises against production use, but to get going, just add this line to your config/environment.rb and sync up the gems (making sure you have GitHub as a source, first):
config.gem 'burke-monkeysupport', :lib => 'monkeysupport', :source => 'http://gems.github.com'
Burke's only tackled a little bit of ActiveSupport so far but has found a runtime decrease of about 75% on average, even with the calling back and forth taken into account. He's keen for other people to get involved, fork MonkeySupport, implement other parts of ActiveSupport, and send pull requests to him. I'm not sure about the viability of this technique in the long term and hope to look into it further for a Ruby Inside feature.