Drupal contrib modules can cause memory and CPU usage increasing to unseen level till the White Screen of Death appears.

The most obvious solution is: on a production site, disable any module you can. Devel module and other administration tools should be disabled to lower memory usage.

Here some suggestions to solve this problem:

• Server indigestion: The Drupal contributed modules “open buffet binge” syndrome
• Measuring memory consumption by Drupal bootstrap and modules (with benchmarking patch)
• Appeal to all developers and contributors for low memory modules on drupal.org

About PHP accelerators:

• Alternative PHP Cache (APC) on Wikipedia