This is a quick reminder that if you are deploying custom applications on servers other than where you install CRM, you need to manually install WIF (Windows Identity Foundation). These pieces are not included in the .Net Framework 4. Here is a sample error message you may receive if you run a custom application without WIF installed.
You can download and install the appropriate WIF from here. I also noticed that Microsoft upgraded the download site for this piece. You no longer need to know what OS you are on to download the appropriate file.