White Sands National Monument is just about an hour's drive outside of El Paso and well worth the trip. Part of the excitement for those who've never visited is the anticipation of seeing a vast swath of sand in the middle of the Southwest desert. You'll pass through the Missile Test Site on your way there, and before you know it, you see a waterless beach in the middle of nowhere.
Once you enter the park, it's pretty surreal to be in the middle of these giant gypsum dunes. You can rent sleds at the visitor center and slide down the dunes, which we highly recommend. There are campsites in the park as well, which we unfortunately didn't have the chance to stay at but hope to return someday, tent in hand.
More pics of White Sands National Monument, along with pics of our entire West Texas adventure, are on our flickr feed.