If you plan on publishing your project, you will likely need a developer account.  Many of these require that you have a mail account associated with their authentication method.  Here’s a few pointers on where I’ve gone to sign-up.

Android Developer – Google Play (https://play.google.com/apps/publish/)

Windows Development – Windows Store (https://appdev.microsoft.com/StorePortals/en-us/Home/Index)

Windows Azure – Cloud Computing / Storage (http://azure.microsoft.com/en-us/)

Network Solutions – Domain Registration (http://networksolutions.com)

YouTube – Videos, Demonstrations and Tutorials (http://www.youtube.com/yt/creators/)

WordPress – Blogs (http://wordpress.com)

You may know of others.  This is the list of ones I’ve recently frequented.