Installing MySQL gem with MySQL 5.0 +

On Mac:
sudo env ARCHFLAGS=“-arch x86_64” gem install -no-rdoc —no-ri mysql - —with-mysql-config=/usr/local/mysql/bin/mysql_config

On Windows:
gem install -no-rdoc —no-ri mysql – —with-mysql-config=“C:\Program Files\MySQL\MySQL Server 5.1\my.ini”

On Ubuntu:
sudo apt-get install libmysqlclient16-dev
sudo apt-get install ruby1.8-dev
sudo gem install mysql
(from http://www.searchmarked.com/ubuntu/install-ruby-on-rails-in-ubuntu.php )
(find the most recent libmysqlclient here: http://packages.ubuntu.com/search?keywords=libmysqlclient&searchon=names&suite=karmic&section=all)