Don Cooke, author of Fun with GPS, had some of the best slides in his talk at Where 2.0. His talk was about how GPS helped emergency responders navigate New Orleans following Hurricane Katrina and the resulting flood.
His company supplied several hundred Tomtom car navigational units, free, so National Guard helicopter pilots could find city locations (helicopter nav systems operate on lat/lon, not addresses) and boat pilots could navigate downtown.
In addition to this effort, Don also spends a lot of time hacking on and playing with GPS devices:
He showed some pictures of his fun side-projects such as: GPS-enabling his cat:
"In the southwest corner, she spent a lot of time looking for that mole in the flower garden."
And the result:
Doing side-by-side comparisons of Tomtom and a competitor's unit:
The two units show conflicting advice: "turn left" and "turn right." Don: "which way did I go? Straight, of course."