For ASP.NET questions check:
http://blogs.crsw.com/mark/articles/254.aspx
http://www.geekinterview.com/Interview-Questions/Microsoft/ASP-NET
For C# questions check:
http://blogs.crsw.com/mark/articles/252.aspx
For SQL Server 2005 check:
http://www.techinterviews.com/?p=161
For ADO.NET questions check:
http://www.geekinterview.com/Interview-Questions/Microsoft/Ado-NET
http://www.geekinterview.com/Interview-Questions/Microsoft-NET/Ado-NET
Most interviews are not that technical. They ask you about the nature of your previous job. What projects have you worked on. Can you do this... how can you do that? Hence be prepared to explain the architecture and the functionality of your previous projects.
Make sure you use the proper technical terms when speaking. This is a way to point out how much the person being interviewed is technically educated.
Be prepared for questions such as "What benefits does SQL Server 2005 provide over SQL Server 2000" , or how does ADO.NET 2.0 differ from ADO.NET 1.1 or from ADO...
If you're applying for a web development position, you might be asked about web standards, XHMTL, CSS, even Javascript...
The possibilities are endless.
Hope this helps