Reddit reviews Edible and Useful Plants of Texas and the Southwest: A Practical Guide

Delena Tull's book on edible plants is a classic--- I suggest a copy of it if you are interested in the subject.

One of the things that people tend not to collect and use are acorns. I made about 20 pounds of acorn flour last year and make muffins and biscuits with it 50-50 with wheat flour. Acorn flour can cost up to $20 per pound if you can find it. I make mine mainly from trees near town lake. Takes time but it's very worth it.

http://www.amazon.com/Edible-Useful-Plants-Texas-Southwest/dp/0292781644

http://www.wildflower.org/collections/collection.php?collection=centex_edible

http://www.foragingtexas.com/

Not sure about desert plants exactly, but I've found the kind of resource you're looking for for my area. Texas is pretty arid so perhaps some will be useful:

http://www.foragingtexas.com/

I also bought a good book on the subject a few years ago that I recommend:

Edible and useful plants of Texas and the southwest