New on the front page is a http://the-w.com/popthreads.php which will take you to a snapshot of our last 24 hours' worth of referrals. Every thread which has received at least 5 hits from the Internet outside within the past day will be listed on the page. Clicking on linkified referral numbers will break out the day's hits if you're that bored. (All this is assuming I haven't made any programming errors - always a 50/50 prospect)
The "popular threads" link will show up whether you're logged in or not, and shouldn't be confused with the "hot threads" which pop up at the top of the front page when a threshold is crossed representing a certain number of replies in a certain period of time.