Tons of info and links:
http://gpsinformation.net/

GPS Tutorial:
http://www.mercat.com/QUEST/gpstutor.htm

 

Garmin:

http://www.garmin.com/

 

Hertz in-car GPS review (short):
http://www.pcworld.com/howto/article/0,aid,109560,pg,1,00.asp