ASP.NET 2.0 Health Monitoring
Health Monitoring is an amazing api now out of the box in ASP.NET 2.0. It can help you in various ways if you are a administrator trying to fine tune your application or a developer looking for an issue. After reading up on this, I had to post a little about it. My favorite feature is the ability to extend of the System.Web.Management.WebBaseEvent class and create your own personal application monitors. You just raise a small event say everytime the user reaches an error page. Sending email alerts is already built in so dont ask that question. You can even dump alerts to SQL Server. I would then make and admin section that just gave me a gridView of this information. The link below provides an overview and even describes how you can make your own events like "long SQL Server Times" or "dllSlowCompilation". Im sure you can think of better ones :).