A state by state guide to sunsets
Yahoo! Travel has put together a guide to sunsets in all 50 states. There are some predictable locales, including Cannon Beach in Oregon and the Smoky Mountains in Tennessee.
Oklahoma's selection is the Wichita Mountain Wildlife Refuge near Lawton. That's a good as any in the state but any flat open space will do. We may not be blessed with mountains here, but we have some pretty spectacular sunsets just about everywhere in the state.