Nice website showcasing what's left (and what's been lost) of Oklahoma City's modern architecture by a local preservation group:

OKC Mod (http://okcmod.com/)

Some photos:

Otologic Medical Clinic

http://okcmod.com/wp-content/uploads/2012/09/image0053.jpg

What's Now The Classen:

http://okcmod.com/wp-content/uploads/2012/09/citizenstower.jpg

State Capitol Bank:

http://okcmod.com/wp-content/uploads/2012/09/image0231.jpg