Performance Monitor. I use the numerous counters available to monitor server, database, application, CLR, etc. I use SQL Profiler and Execution Plan statistics too during unit testing. Any specific information you are looking for?
Yes, take a look at the following: http://www.aspheute.com/english/20000809.asp http://aspnet.4guysfromrolla.com/articles/041002-1.aspx http://www.codeproject.com/KB/dotnet/perfcounter.aspx There are many examples on the web on using performance counters. Add a flash-based graphing component or other graphing package and you have some hot looking counters on the web via ASP.NET. Good luck!