VERY cool! A few bits of advice:
1. Take a look at
http://www.maptools.com to learn about UTM coordinates and using grids to allow your GPS to work with paper maps.
http://www.mytopo.com is a great topo map service.
2. If you don't already have one, invest in the cable that allows you to connect your GPS to a computer, then take a look at the software at
http://www.expertgps.com . This software allows you to maintain/create waypoints & routes via your computer, plus the expert version gives you free access to USGS topo maps and aerial/satellite (?) photos.
3. If you want to use it in your vehicle, consider getting a RAM suction mount for it. They're a bit pricey, but work great, AND they keep your prized GPS from slaming through your window in a panic stop!
http://www.ram-mount.com/ramgps.htm4. Consider geocaching as an excuse to use your GPS and to learn more about it.
http://www.geocaching.com 5. Take a look at
http://www.gpsinfo.com for LOTS of related information.
6. Remember that the magic triad of navigation is a good map, compass, and GPS. A GPS by itself simply will not live up to its potential. Always carry a good magnetic compass and extra batteries along with you.
My favorite book on the topic is
GPS Land Navigation by Michael Ferguson, though it is no longer in print and its review of specific GPS models is certainly out of date. It focuses on using the GPS along with a map and compass. Amazon.com lists several new & used as still available. I'd recommend the investment.