Today I put together one year worth of GPS tracks from my lunch walks and bike rides around the office. The colors correspond to different speeds - yellow is for walking, magenta is for biking and cyan - driving at highway speeds:

In case you feel offended by the bright neon colors, here is another version (blue = walking, green = biking, red = driving):

If you have tons of GPS tracks and want to visualize them, the tool I’m using is here: http://avtanski.net/projects/gps.