Authenticate external users to Sharepoint 2010.

Here is an article briefing the way to create a custom Trusted Identity Provider using the new Windows Identity Framework in Sharepoint 2010.

http://stefvanhooijdonk.com/2010/08/19/writing-your-own-trusted-identity-provider-for-sp2010-1/

Using this provider, external users like Users in a Sql Server, Facebook or any source will be able to login to Sharepoint 2010 and not just AD users. Cool!