How do I figure out where this blast of traffic to my website is coming from?

I made a small pet project (that doesn't even seem to have proper SEO tags) called p4kprowler (http://p4kprowler.meteor.com) which helps you sift through Pitchfork album ratings.

I made it around July. Showed it off a little bit of Hacker News, and over here on some niche sub-reddits. Tested out a google adwords using this site, didn't bring in anything substantial. I was averaging out 100 hits a week, which I still thought was pretty cool.

Now here's weird part that I have no explanation for.

All of a sudden on Sunday, I got 585 hits. I had 22 on Saturday. And on Monday that number nearly doubled!

http://imgur.com/KSk79vU

All the traffic sources say "direct" hits. I googled for the website, and I couldn't seem to find a trace of ANY buzz for the site. Twitter searches came up empty. Google searches linked back the old threads I had made in July showing the site on Reddit.

Another weird nugget of information that may be useful is that a good majority of the hits are all stemming from Cincinnati.