Returning from New Mexico on our trip in April 2007, we traveled along Interstate 40 through Oklahoma. We stopped at the welcome center and asked what there was to see and do along our journey. The lady behind the desk, with a glazed over look in her eyes, just handed me a state map and never said a word, so we continued on our journey. Here's what we saw:
This.
And this.
And a lot of this.
I'm sure there's a lot more to see in Oklahoma, but we'll have to try and find it on our next trip. From Oklahoma, we continued to Arkansas.