There are plenty of cool GPS data projects in existence, but this is one of the most beautiful I've seen: three whole years of location data, taken from an iPhone.
To make it, Aaron Parecki collected the location from his iPhone every few seconds for over three years. Then he turned his data into a map — it's Portland in the US, if you're trying to work it out. He explains:
"Approximately one GPS point was recorded every 2-6 seconds when I was moving, and these images represent about 2.5 million total GPS points. Collectively, they represent a data portrait of my life: everywhere I've been and the places I've been most frequently. The map is colored by year, so you can see how my footprint changes over the years, depending on where I live."