Just got my Ubuntu box up and running with Fiesty Fawn and installed MySQL server (5.x). The default server does not allow, the MySQL server to be accessed remotely. Besides adding the user to user's table in MySQL database, I had to additionally edit my.cnf file in /etc/mysql and change the following setting:
bind-address = 127.0.0.1
bind-address = 0.0.0.0
The IP of 0.0.0.0 allows incoming connection from any host and of course you need to make sure there is not firewall in between blocking the port 3306. Since all this setup sits behind my Linux firewall it is pretty secure and allows me to develop my ROR apps from the windows box by accessing MySQL databases on another machine.