Logging Application Block & 'The Heisenberg Uncertainty Principle'
The recently released Logging Application Block in the 'Patterns & Practices' MSDN series hits a home-run. It's better to insert instrumentation in the application during its development than trying to retrofit it post-deployment. Also, plan out thoroughly the application exceptions and metrics. I recall encountering a monitoring application that would gather more monitoring data than all the deployed applications' data combined - an example of 'The Heisenberg Uncertainty Principle'.