Naps save me every time. Just when my work starts flagging and quality starts dropping, a 20min nap makes me feel almost as fresh as I am coming into the office in the morning. Most others at work feel awkward about taking naps - even with me evangelising naps :o)
I have to admit, I'd feel awkward taking naps in my office. What I usually do is go to my car in the parking garage and nap there. It works wonders; I recognize that the 15 min that I lose to the nap would have been lost to my brain being a foggy mess, so the nap is a net gain.
My wife has done the napping in the car bit earlier in her career.