What do you use to monitor your web application?
dpritchett: I have trouble imagining something more useful than Munin for a *nix server.  Check out this screenshot - it only shows four of the tens of graphs available at any given time: http://dpritchett.posterous.com/test-driving-munin-service-s...Edit:  Munin profiles services and responsiveness.  You'll probably want to complement it with Nagios to monitor service/hardware failures.