I have installed the Windows Identity Foundation but can\'t find the Microsoft.IdentityModel dll. According to the Azure Hands-on-Labs it should just be in Add Reference in
How about a NuGet Windows Identity Foundation. Just add it you you project and away you go! Its one of the MS owned NuGets so should be maintained accordingly.
EDIT: In Windows 8 Windows Identity Foundation is installed (enabled) by turning a windows feature on in Control Panel > All Control Panel Items > Programs and Features > Turn Windows feature on or off the feature is Windows Identity Foundation 3.5. Installers linked in the answer above will not work on Windows 8