I actually don't keep my soap in the shower. I keep a few bars in some dishes around the corner from the shower, so they have plenty of drying out time between uses. In my shower, it is impossible to leave a bar of soap within the shower stall and expect it to stay dry until the next time I want to use it. Partly this is because of the design of our shower, and partly this is because I don't shower as often as my husband, so the soap would get wet more often than it is used.
Sink-side soap is another story. Each of our bathrooms and the kitchen sink all have at least one soap dish with at least 3 different soaps for testing purposes, but that is the least because it's in the smallest bathroom that has little sink-side space. The others have at lest 2 soap dishes with even more soaps for testing purposes. The one upstairs has even more because it has more space. My sink-side soaps tend to be of the guest-size or travel-size variety. Of course each soap dish has an insert to allow for thorough draining and drying out between use.
So the bottom line is, how many different soaps are actually out at my house? I couldn't even tell you unless I started walking around the house and started counting! Off the top of my head, I'd say it's easily 2 dozen.