ASP.NET 2.0 and VS 2005 add a bunch of features that make localizing ASP.NET applications much easier.
To learn more about how the localization features work, I'd recommend first checking out this excellent 13 minute video in the ASP.NET 2.0 "How Do I?" video series. In it Scott Stansfield walks-through how to build and localize an ASP.NET application from scratch, and how to support both dynamically picking the language used based on the incoming user-agent string of the client, as well as allowing a user to explictly choose their language preference from a dropdownlist. I think you will walk away being surprised at how easy it is.
Wei-Meng Lee has also written a great walkthrough article on ASP.NET 2.0 localization that you can read for free on the O'Reilly network here. For more detailed information on ASP.NET 2.0 localization, you can also then read Michele Bustamente's excellent ASP.NET 2.0 Localization article on MSDN. Bilal Haidar also has a great artlce on ASPAlliance here.
The articles and videos above use XML .resx files to store localized resource strings. These can either by compiled into binaries or deployed as XML source with an ASP.NET 2.0 application. Jeff Modzel recently published an article that shows how to build a custom Resource Provider that stores the resource strings in a database instead. You can read about how he built this as well download his sample code here.
Hope this helps,