So what's this all about? It seems that, in the coming weeks, YouTube plans to launch a brand-new user interface for their Channels section and if you click the secret link, you can be a part of the group that helps test it and provide feedback.
The secret link's URL is (hilariously): http://www.youtube.com/super_seekrit. Once you click that, you'll be taken to a web page that welcomes you to the secret Channels beta program. The page also warns you that this is experimental so some things may be broken while other things may just be incomplete. If you don't like the beta design, you can switch back to the old layout by clicking the "opt-out" button.
Here's the message that displays:
The new Channels section lets you edit your Channel within your channel. Using buttons at the top of the screen, you can change "Settings," "Themes and Colors," and "Modules." Previously, this type of editing had to be done on a separate page. Also, an "edit" button appears within different sections of the page, letting you further customize those particular parts.
Here's what the current Channels section looks like:
Here's the new Channels beta:
YouTube has also set up a "secret" blog which they'll use to communicate with the beta testers. You can follow the blog here: http://youtube-channels-beta.blogspot.com. There, you can leave bug reports, requests, and other feedback in the comments section.