Google Analytics is used for usage tracking and may drop a cookie on you. I've set my account to not share tracking data, but you have no way to validate that and I have no way to confirm that Google honors this setting.
Other external resources are referenced, including Twitter's scripts for explicit pop-ups and Microsoft's CDN for jQuery. On the homepage a few extras are loaded: JSON and assets from Tumblr and a Flickr script which insists on loading a Yahoo geolocation script as well as requested assets. None of these should be using this to track you, but my control is limited so YMMV.
All original work is licensed by Hans Gerwitz under CC BY 3.0.