I don't think Dan needs any help yelling in our newbie ears.
Actually, the more serious suggestion is a great idea, but it seems like it would be a lot of work for an admin or moderator to keep track of the topics that have been gone over and dig them up in order to create links to them. If it's not practical, I think the only thing to do is encourage members to provide as much detail in the subject line so that one can make a decision as to whether one wants to join in a topic without actually reading the first post. If you find it annoying or repetitive, ignore it. I think a lot of members are doing that to a certain extent; you don't see a lot of response to topics like "PC or not?", and when there is extended discussion it seems to become tangential rather quickly.