The manufacturers website Garmin.
Garmin make several ranges of GPS receiver.
The eTrex range is arguably the most popular. A comparison chart of the models can be found Johnny Appleseed's Comparison Chart.
Garmin symbols can be changed for many models. Instructions can be found here - Geocaching Symbols on a Garmin GPSr
(add more if you want)
MapSource is Garmin's mapping software