I was having trouble with a webserver this week, which I'd just set up for a client. When it went live, it seemed OK initially, but when we left it overnight it curled up its toes and died. It was so dead that I couldn't even ssh in to reboot it, so we had to do a remote reboot. Crunch.
Anyway, on getting it back up, I poked around in the logs and found that it was running out of memory, which it really shouldn't do given that it was a fairly low load on the webserver, and only apache, mysql and php were running on it. I looked around the Interwebs and found an excellent resource called Troubleshooting Memory Usage, which gave me some pointers about how to rein in apache and stop it from eating up memory so quickly. Thanks!
Anyway on the page was a script for summarising memory usage, which I thought was a good idea, so i grabbed that one and adapted it to my own purposes. I thought I'd make the results available here, so feel free to grab it and adapt it to your own needs.