Tuning MySQL to consume less memory
MySQL should include a number of starting point configuration files for my.cnf that can adjust the memory usage. The files are named my-small.cnf, my-medium.cnf, my-large.cnf, and my-huge.cnf.

There is an online MySQL memory usage calculator at http://www.mysqlcalculator.com/. By comparing the starting point files and using the memory usage calculator you should be able to adjust your my.cnf configuration file to accomodate your server's memory constraints.

For more information about what each parameter does, you can reference the MySQL documentation available online. Here is a link to the MySQL documentation for MySQL server 5.1: http://dev.mysql.com/doc/refman/5.1/en/server-system-variables.html