If you're looking for an Add To Favorites Module, you've really got two choices.
MyLinks, (available here) lets registered users store their favorite local links in a basket so that they can easily go back to the parts of your site they like the most. You need to install both the component so that you can handle the back-end management and the module so that users can see it.
The other option is the jh_Favorites (available here). This has some nice features beyond simply adding a page to a favorites list. It also checks whether the user has already added that page and tells the developer how many times a page has been added - a good measure of which topics your users like. Best of all, the link appears automatically at the end of each article, saving you the trouble of doing it yourself.