It's not surprising that a place as great as Enchanted Rock has a few mentions on the World Wide Web. Here are some of those [along with some comments that I'll probably regret later].
Texas Parks and Wildlife have their own WWW site for Enchanted Rock, which they have recently . The site provides the basic info you'll need about the park. There is also information available on the equally crowded (and almost as geologically interesting) Inks Lake State Park.
Ira Kennedy provides his "Visitors Guide to the Center of the World", and the archives of the late, lamented Enchanted Rock Magazine.
"Wild Texas" provides ER info and has some Quicktime movies that I wish I had put together first.
The official web site of the town of Llano has a few things to say about ER.
TopRope.com (climbers' site) has an E-rock page.
Enchanted Rock State Natural Area Repeats all the old INCORRECT INFORMATION that used to be on the TP&W page