You'd be surprised at how often the problem of resetting the mysql root user account comes up in the freenode #mysql irc channel. People are always referred to the online manual directions, but most can't successfully follow them. I wrote up this quick and dirty summary. This assumes you are at a local shell and that having the database exposed temporarily without account password protections is not an issue. If it is, unplug the ethernet cable for a bit:

Reset Mysql Account Root Password
The easiest way is to

• stop the mysqld service
• add 'skip-grant-tables=1' to the my.cnf configuration file under the [mysqld] section
• start the mysqld service
• connect using 'mysql -u root'
• do 'use mysql;'
• do 'update user set password = PASSWORD('new_pwd') where User = 'root';'
• stop the service again
• return my.cnf to its original condition
• restart the mysqld service
• test with 'mysql -uroot -p' and enter your new password at the prompt

...of course, I have always suspected that access issues in mysql serve the same purpose as the calculus requirement in college CS departments. To weed out the unworthy. ;^)