An Introduction To Performance Counters

http://www.codeproject.com/dotnet/perfcounter.asp

http://msdn2.microsoft.com/en-us/library/fxk122b4.aspx

Performance Counters (IIS 6.0)

Displaying Performance Monitor Information through an ASP.NET Web Page, Part 2

http://aspnet.4guysfromrolla.com/articles/041002-1.2.aspx