Now we are five
Keep in mind that an API for Google Maps did not yet exist. This was the first act of its kind to mash data up and add it to a Google Map and as far as record keeping goes, is, the first Google Maps hack, or mashup. I've always tended to call it a hack since it's just more bad-ass and disruptive than a "mashup" sanctioned by a proper API. :)
I think we can hold our heads up as reasonably early adopters - our first serious project, a homicide map backdated to the beginning of the year, launched in mid-2005, a collaboration between editors Brett Smith, Chris Carter and me.