I stumbled upon this little tidbit & decided it was reposting here. If you create a file in an ASP.Net 2.0 application named app_offline.htm it will bring down the appdomain & just return the contents of that HTML document!
Make sure your HTML page is at least 512bytes in size, or IE's "friendly errors" may eat it. :)
The MAJOR benefit I see here is that you can quickly rename a standby page to app_offline.htm, make a few changes (replace locked files, etc) & then rename it back to app_online.htm & you're back in business.