Stealth activities which were requested in Moodle tracker a long time back since 2006 are coming soon in Moodle and currently under peer review process. A prototype to test out the functionality of stealth activities is setup at Moodle Prototype site here.
Stealth activities are those activities which are accessible to students, but not listed on the course front page. The course creator will manually put a link to the activity somewhere else in the course and the activities would be available by following URL but hidden from the course page.
On the frontpage of your Moodle site stealth activities are possible both on the page and in the main menu block but not in the course page. However, you can find a way around by adding as an orphaned activities but now after this development you may not use orphaned activities in future. When this tracker issue is implemented in Moodle core then Gradebook, recent activity and other blocks will also display “stealth” activities!
While editing any page resource on the prototype site you will find “Hide on course page” under the visibility settings apart from the default Show and Hide.You can check out the progress about the Stealth activities in this Moodle Tracker issue – MDL-4782 and check out the prototype at http://prototype.moodle.net/stealth
Let us know how you found the stealth activity prototype in the comments below.