We use NewRelic to see everything from the bottom up: http://newrelic.com/ http://newrelic.com/ It's really easy to use, comprehensive and they have a 14day tr

We use NewRelic to see everything from the bottom up: http://newrelic.com/ http://newrelic.com/ It's really easy to use, comprehensive and they have a 14day trial. I also like yslow: http://developer.yahoo.com/yslow/ http://developer.yahoo.com/yslow/ It's good for quick checks.