I log tracks damn near everywhere I ride. The cool thing is you can select-all, pull them into Google Earth or wherever, and see everywhere you rode in an area over a season. Another cool thing you can do with those tracks... geo-tag your photos. Track log is a list of date/time-stamps with lat/long/elev attached to them. Cameras time-stamp photos. Ther'es software out there that'll pair the data between the two. For places I rarely ride and don't know well, it's nice to go back and look at tracks/pics and see what's where. Build a saved track with a few points over the main trails and push them to the GPS.