At the bottom of the form when you're posting is a place for "tags." In case you're not familiar with them, tags can be used to help identify and track topics. If you enter tags for your posts, they'll be grouped with others of the same topic and the most popular ones will be listed at the upper right (which probably will be moved in the future! Someone remind me to edit this post when it happens?) Anyway, when you click on a tag there, all the posts with those tags will be displayed.