Microsoft have made available a security development starter kit at http://www.microsoft.com/security/sdl/getstarted/starterkit.aspx
Actual Download is at http://www.microsoft.com/downloads/en/details.aspx?FamilyID=0FCBA3C7-BC30-47B0-A2F8-2E702720998A&displaylang=en
The kit is free and covers a variety of security concerns for ASP.NET developers.