I've always wondered about this. Since Reagan at least, presidents do seem to return the salutes of uniformed personnel. But is this appropriate? Presidents are civilians and they're never in uniform.
NYTObama Tries Out His Salute
By Jeff Zeleny
KAILUA, Hawaii – He’s not the commander in chief yet, but was President-elect Barack Obama briefly practicing his salute on Sunday?
On the first morning of his vacation here, Mr. Obama arrived at the Marine Corps Base Hawaii for his daily workout. As he walked out of the Semper Fit Center, his gray T-shirt soaked in sweat, he lifted his right hand and gave a quick salute to two Marines in fatigues who were standing in the distance.
The brief moment was not captured by cameras. Photographs and video were not permitted to be taken on the military base, according to campaign aides.