I just found a really nice document on Security Practices for ASP.NET 2.0. Just have a look at the Index of practices to see how much good stuff these people have put together!

Security Practices: ASP.NET 2.0 Security Practices at a Glance
J.D. Meier, Alex Mackman, Blaine Wastell, Prashant Bansode, Andy Wigley, Kishore Gopalan
Microsoft Corporation
August 2005

Summary
This module presents a set of consolidated practices designed to address ASP.NET version 2.0 security issues. The answers and recommendations presented in this module are designed to supplement the companion modules and additional guidance. The practices are organized by various categories that represent those areas where mistakes are most often made. This module includes an index of practices.