Resources for Performance Monitoring
In the past I would have been digging for hours through performance monitor logs looking for interesting spikes or patterns.
Now there's a scripted tool you can run on the logs files while you are off making a coffee:
I recommend downloading and watching the hour-long LiveMeeting training (Note: the "Watch Online" link won't work; I'll get that fixed or removed).
Have a look at Clint Huffman's blogs too: