I've recently gone through a phase of getting off to stories my wife tells me about seeing her girlfriends undressed, either in the locker rooms at work, at sleepovers or in clothing store changing rooms.
There are a couple of her closest friends who I know quite well - and the times that have really got me going are when she's described them naked to me. It's great meeting up for dinner or popping round for a cuppa and knowing they're shaved or have intimate piercings