When you switch on the "saved listings" switch at Admin Panel -> Settings -> Switches, an option appears in the listing tools tab bar and the listing bit tools of each listing which the user can click on to save the listing for future reference. This offers an easy way for your visitors to keep track of their favorites. By default this only appears for registered members, not unregistered guests, but it can be enabled for guests as described in the bottom section of this article. Once saved, the member can go to their member home options area and will see a "Saved Listings" tab on the left which when clicked will display a compact list of the listings they've saved. They can also use that page to remove saved listings from their list.
Once the switch is on, the "saved listings" template will become visible in your template editor (Admin -> Themes -> Manage Templates) so you can customize the appearance of that page.
If you wish to make saving listings a special privledge for sponsored usergroups, you can use the Admin Panel -> Members -> Manage Usergroups page. Select any group and look for the "can save" checkbox in the Listings section to choose whether that group can save listings.
The saved listings utility is for allowing people to build a favorites collection. Unlike the member personal listings list option, it won't allow them to add anything to the list which doesn't already exist on your site.
Guest Saved Listings
To enable saved listings for guests, you must be running WSN 9.1.27 or later. Go to Admin Panel -> Members -> Manage Usergroups (or Admin Panel -> Settings -> Manage Usergroups if you've disabled membership) and click the Guest usergroup. Under Listings, check the "Can save" box and save your changes.
Guests don't have a member home menu on which to find their saved listings, so you need to add it to the main menu. Go to Admin Panel -> Customizations -> Menu Manger and add a new menu item to the main menu titled something like "Saved Listings" or "Favorites" with the URL savedtopics.php.
Note that guest saved listings won't work in Internet Explorer 6 or 7, but those browsers have less than 1% marketshare.