If you find an interesting forum discussion you'd like to keep track of, you can use the built-in feature to follow it. When you follow a discussion, you'll receive an email whenever there is a new reply to the discussion. This email notification will contain a link to the new reply.
To follow a discussion, go to the page for that discussion and click the link to "Follow - Email me when people reply." If you're already following a discussion and would like to stop doing so, this link will appear as "Stop Following". Clicking that link will stop email notifications about new replies to the discussion.