From MSDN mag, here is a list of 5 deep dark tidbits from ASP.NET.

I ran across this when searching for more info about the __code keyword. Found out that __code will point to the assembly generated for the App_Code directory. When porting my ASP.NET 1.1 project to 2.0, I have a need to find the App_GlobalResources assembly. I have hacked my way around a way to find it, using typeof(Resources.SomeFile).Assembly) but would be great if there was something like "__GlobalResources".

Anyway, this writeup by Jeff Prosise
Wicked Code: Five Undiscovered Features on ASP.NET 2.0 -- MSDN Magazine, February 2005
talks about the following:

• Updating browser displays without refreshing page (AJAX-isms)
• Encrypted configuration sections
• Auto culture handling (Culture="auto" in page directive, get date formats, etc on the page localized on the cheap)
• Custom expression builders - very cool. Used to load resources, appSettings data, etc. (<%$ AppSettings.MyText %>
• Custom web events