Traxplorer is a Google app I've found that seems to be pretty cool. It's easy to view tracks you've created elsewhere but maybe want a better map layer than you bought with your GPS unit. You can also view the tracks you created on your smartphone using Google's My Tracks app. And then of course you can also view the Google maps formats of KML and KMZ. I'm still figuring it all out. It seems to like gpx but not gdb formats.