Show post titles but not content.

I am setting up a membership site with three levels: visitor( non-member), regular (registered non-paying) and premium (paying). Premium members have access to a few categories unavailable to regular members. That is set up and works well.

I would like to make the titles of posts in these categories available to everyone so that they can see the posts and frequency unavailable to them. A category widget could work just fine. The membership plugin would then prevent access to the post should a non-premium member attempt to access it.

Can this be done? If so, how?