I use a
Garmin eTrex Camo . All though a bit basic on features, it has served we well and has decent battery life.
When hooked up to a laptop or PDA and
Microsoft Streets and Trips (Windows) or
GPS Drive (unix) it makes a great
navigational aid. It managed to get me around California/Nevada last summer, with only one missed turn (the road
signs were wrong, honest
).
If you are based in the US I would recommend looking for one that has
WAAS support as this will get you a bit more
accuracy, than one with out