Links: SharePoint V3: Search: Search Center

Adding Properties to MOSS Advanced Search
http://www.codeproject.com/spoint/MOSS_Advanced_Search.asp?print=true

How to: Change the Properties Returned in the Core Search Results
http://msdn2.microsoft.com/en-us/library/ms560074.aspx

How to: Display a Search Scope in the Search Box and Advanced Search Web Parts
http://msdn2.microsoft.com/en-us/library/ms498872.aspx

Walkthrough: Add a Tab and Custom Search Page with Enterprise Search Web Parts to the Search Center
http://msdn2.microsoft.com/en-us/library/ms584031.aspx