Texas Forest Service interactive Tree Identification Guide. Excellent site with great graphics and an interactive visual key. Also lots of information about growing trees, invasive species, and making a leaf collection.
Texas Native Trees – Based on Benny Simpson’s book “A Field Guide to Texas Trees,” this website has great photos and growth characteristics for hundreds of native Texas Trees.
The Texas Forest Service maintains the Texas Big Tree Registry. The goal of this program is to locate and recognize the largest known species of its kind that grows in the state of Texas, and to stimulate public interest in trees as a resource.
Tree Planting Guide for Bastrop, Caldwell, Lee and Fayette Counties, produced by the Pines and Prairies Land Trust, in cooperation with the Texas Forest Service. (Includes trees available at nurseries, not all native).