Using Visual Studio 2012's ASP.NET Tools for Windows Azure Active Directory you can easily set up your ASP.NET applications so that they can authenticate against your Office 365 domain. If you're an Office 365 user, this is a great way to allow your existing Office 365 users authentication functionality against your custom ASP.NET applications. This video walks through the process of setting this up. In under 4 minutes, you'll see how to build an Office 365-connected site that can be deployed to Windows Azure Web Sites.
- Vittorio Bertocci's blog post on the Windows Azure Active Directory tools for ASP.NET
- Link directly to download the tools for Visual Studio 2012