Sharepoint Application Pages

Custom application pages in the SharePoint 2010 Sandbox

http://www.wictorwilen.se/Post/Custom-application-pages-in-the-SharePoint-2010-Sandbox.aspx

SharePoint: Application page to display all sites a user can view

http://techtrainingnotes.blogspot.com/2010/02/sharepoint-application-page-to-display.html

MOSS 2007

http://weblogs.asp.net/soever/archive/2006/11/09/SharePoint-2007-_2D00_-_2F005F00_layouts-and-how-to-create-pages-that-run-in-site-context.aspx

WSS 3.0

http://msdn.microsoft.com/en-us/library/bb418732(v=office.12).aspx