Server Overload Fix & PHP Optimization

My newly-redesigned product catalogue site has been crashing the virtual cloud server it lives on. The load climbs rapidly until the kernel’s OOM-killer steps in, MySQL gets shot down, and Apache stops responding... (Budget: $30 - $250 AUD, Jobs: Apache, Cloud Computing, LAMP, Linux, MySQL, Performance Tuning, PHP, System Administration, Troubleshooting, Web Hosting)