site multisite

My current website home, sometimes loads very, very, very slowly. I have rebooted my server once and it sped it up, but I am wondering about some best practices to optimize drupal performance on the backend. I have a lot of memory intensive modules, so I think that may have something to do with it.

I've been digging through the drupal planet trying to find anything, but wondered if anyone else has had any issues with slowness.