Reference for custom claims provider

Understanding People Picker and custom claims providers

http://blogs.technet.com/b/tothesharepoint/archive/2011/02/07/new-understanding-people-picker-and-custom-claims-providers.aspx



Custom claims providers for People Picker (SharePoint Server 2010)

http://technet.microsoft.com/en-us/library/gg602072.aspx



How to: Create a Claims Provider

http://msdn.microsoft.com/library/ee537299.aspx



Claims Walkthrough: Writing Claims Providers for SharePoint 2010

http://msdn.microsoft.com/library/ff699494.aspx



People Picker overview (SharePoint Server 2010)

http://technet.microsoft.com/en-us/library/gg602068.aspx



Claims Walkthrough: Creating Claims Providers for Trusted Login Providers for SharePoint 2010

http://msdn.microsoft.com/en-us/library/gg251994.aspx



Replacing the out of box Name Resolution in SharePoint 2010 - Part 2

http://blogs.technet.com/b/speschka/archive/2010/05/17/replacing-the-out-of-box-name-resolution-in-sharepoint-2010-part-2.aspx