It figures. I'm supposed to leave on Friday for Norway and I waited until today to check the expiration date on my Passport. It expired in January of this year. That gives me 3 days to try to get it renewed before my flight takes off. This site makes it look like it ain't gonna happen, but I'm hopeful. There's a fair amount of walk-in places in Denver that do on-site photos.
Let me know if you have any tips or have been through this process yourself.
Update: Thanks to David Carter's suggestion, I found American Passport and should have a new passport on my doorstep Thursday morning.
Update 2: Passport has arrived!