In recent months I've been working on a pet project - a .NET 2.0 library which encapsulates Yahoo! Mail's SOAP web service with an object oriented design. Instead of working with a flat list of methods, developers can work with objects like Account, Folder, YMessage and so on, all organized with conventions familiar to every .NET developer. Since the Yahoo! user authentication method requires redirecting from the web application to a Yahoo login page, and then back to the web application...