Sharepoint Apllication Development Types

Application Development on MOSS 2007 & WSS V3

http://blogs.msdn.com/b/cjohnson/archive/2006/09/05/740498.aspx

How to: Create a Custom Application Page (i.e., Host a Custom ASP.NET Page) inside of a SharePoint/MOSS 2007 Portal
Creating an Application Page in Windows SharePoint Services 3.0
Getting Started with SharePoint 2010