I found this article from MSDN to be a good introductory resource for working with State Management in ASP.NET 2.0. Since I’ve been developing WinForms apps for over a year now, and haven’t done any ASP.NET since 2004, I found this to be a good refresher.
This is a good introductory article for WinForms developers moving into Web Application development, especially those working in 3(+)-tier architectures since you now have to do something with your business objects in the event that a postback occurs.