For organizational or corporate account scenarios I recommend looking at leveraging Azure Active Directory. You can find out more about how to do this on Vittorio Bertocci's blog:
Daniel Roth is a Senior Program Manager on the ASP.NET team working on ASP.NET Web API. Prior to working on ASP.NET Daniel worked on Windows Communication Foundation and he is excited about building HTTP services for the Web. In his spare time he enjoys spending time with his wife and two boys, Benjamin and Joshua.
You can install the ASP.NET Fall 2012 Update preview from here to play around with the features in the update templates: http://www.asp.net/vnext.
You can find the code for the self-hosted Web API here: http://code.msdn.microsoft.com/ASPNET-Web-API-Self-Host-30abca12.
You can find details on the ASP.NET Web API OData support on Alex James' latest blog post: http://blogs.msdn.com/b/alexj/archive/2012/11/02/odata-in-webapi-microsoft-asp-net-web-api-odata-0-2-0-alpha-release.aspx.
Lastly, I will be making the OAuth2 sample code available on the MSDN Samples gallery as soon as I get the code cleaned up later this week.