I have code that references a web service, and I\'d like the address of that web service to be dynamic (read from a database, config file, etc.) so that it is easily changed
As long as the web service methods and underlying exposed classes do not change, it's fairly trivial. With Visual Studio 2005 (and newer), adding a web reference creates an app.config (or web.config, for web apps) section that has this URL. All you have to do is edit the app.config file to reflect the desired URL.
In our project, our simple approach was to just have the app.config entries commented per environment type (development, testing, production). So we just uncomment the entry for the desired environment type. No special coding needed there.