When installing Nokogiri on 10.6 with macports, the build fails because libiconv is missing:
Building native extensions. This could take a while...
ERROR: Error installing nokogiri:
ERROR: Failed to build gem native extension.
/Users/jmacdonald/.rvm/rubies/ruby-1.8.7-p174/bin/ruby extconf.rb
checking for libxml/parser.h... yes