I did some digging, and found out that one address - 126.96.36.199 - had pulled a gigabyte of data down from my site. ARIN.net reports that this address is part of a netblock owned by "Hollywood Interactive". Hmm... I wonder what this could be about.
I checked the web logs, and this host worked through every single link on every single page on my website, downloading every single stitch of data contained therein. It hit login prompts for php apps, worked through every single entry in Gallery at every single possible resolution - EVERYTHING.
I did some poking around, and found that the netblock in question has been implicated in p2p network poisoning, so I have concluded that this was a content scan by the **AA to see if I have any copyrighted stuff on my web site. Yeah, just keep scanning dipshits. Nothing to see here but my son's Cub Scout photos.
Needless to say I made some adjustments to my firewall. No one from that netblock is touching any of my gear again. Bastards.