PastPin by Geopast, challenging the public to geo-locate and time-tag photos of unknown location/time, uploaded by 115 selected institutional contributors to the Flickr Commons.

A nice cleanly designed service for public domain pictures, but page-loading assumes that you have superfast broadband, and that your broadband isn’t already being saturated with other downloads and music streaming. It also seems to be calling images from the often-slow Flickr, which slows it down even further. Lovely idea, but too grindingly slow for the majority of Internet users.