Really there are two types to watch out for, the first type is fuzzy and lives on the ground or in the ground 'wolf' or trap door spiders. Sometimes they make homes in the cracks in wood and walls. It's not so much they are dangerous, but the tend to bite butts of people sitting on their nests.
The other which is everywhere in the Southwest is the Black Widow, it's one you should just leave alone if you see one.
See Chart for dangerous spiders. (not safe for Arachnophobes)
http://3.bp.blogspot.com/-9scyDPFWBI...piderChart.gif
---------- Post added 2013-02-11 at 09:06 PM ----------
[IMG]http://roadtrip.cornick.us/wp-content/uploads/2009/04/mining-i-10-west-of-desert-center-ca-small-300x225.jpg[IMG]
More like this.