Plungers ! We need them, we all agree, but we hate to store them. They shouldn't even be sold without a holder, in my opinion.
Cut a bleach jug, and the bottom of it will make a good place to rest your plunger.
I read that some people like using a terracotta planter, or even just the saucer from beneath the planter.
Some hide the plunger, some store it near the toilet, so someone who needs it may actually find it.
An easy way the clean/disinfect your plunger, is to add bleach to the toilet bowl, after you've unplugged it, and let the plunger rest in the water for a bit.