Q:

How do I add a custom tab to my Facebook profile (not to a page!)?

There are plenty of apps and tutorials out there for adding custom content into a tab for a page.
But how do I add a custom tab to my actual profile?

A:

Facebook removed the ability to add custom tabs to a personal profile page some time ago.  (They can still be added to a Page.)  However, Facebook is in the process of rolling out Timeline, which replaces your personal profile page, and which does allow apps that are specially built for Timeline.  Once you have switched from a profile page to Timeline you will be able to add these apps to your timeline.
Further details can be found here:
https://www.facebook.com/help/?page=105925952849619

