In the gym, as in weight room, as in spreading my cards on the bench between sets. Yoga studios, before or after class--quite common, lots of demographic overlap. In cemeteries--all the time! That's where I hang out. Goth clubs, hip hop clubs, house parties, when I was younger. Cafes, restaurants. The beach, also often. On a boat. Quick two card reading while on a ski lift once. During a Broadway show intermission. In the Everglades! (the deck got water damage but it was okay) On planes, any time I'm in a plane for more than two hours. The library. Parks. Poolside. In the bath.
In a tent made of makeshift materials, on a bed of dried pine needles, during a weekend long wilderness survivalist course. I had to smuggle in the cards as contraband.
I basically ALWAYS have one deck on me, just in case, and to keep working at the list of places I've read.
You never know when you (or a friend, or a stranger) might need a reading...
edit: I've seen a few posts mention haunted hotels and I concur. I mean, if you're there, you GOTTA, right?