mmm that is a permissions issue... and giving logged in users the capability of viewing hidden courses could have a wider implication further into Moodle so that is not a desirable outcome. However, with a little playing around...
In the Front Page Settings there are two options, one for what you want people to see when they visit your page and one that they see after they have logged in. What you might want to do is to create a list of courses you want people to see when visiting, put them into a label to be displayed at the Front Page. When logged in, turn that label off, which can be set in the Front Page Settings, and have a course listing instead, that should take care of that issue without having to change the permissions. Please be aware, I have not tried anything like this, mainly because I never put a course listing on the front page anyway. Since figuring it out, I have only used a label with a table full of icons to visually link the user to the category pages. What I am proposing above though, should work, or it might be more accurate to say I can't think of any clearly discernible reason why it shouldn't. The Front Page Tips and Tricks section might help as well. Anyway, good luck.... and let us know if it does work. Cheers