Here in Pittsburgh, if there is snow on the road and you clear the snow from and around your car in its on-road parking space, you have established de facto property rights over the space. Evidently, Pittsburghers are quite Lockean. (Freakonomics writes about the phenomenon briefly here.)
What's fun about it? It's totally unplanned. Most people respect the fact that if you dig out a parking space, you should enjoy the fruits of your labor. So, people leave a chair or a laundry hamper to show intent to return and use the space. By in large, this system seems to work pretty well here. I get a kick out of seeing assorted wares near the side of the road, but I haven't heard anyone complain about it. (Unlike my neighbors.) Incentives fall to dig out the space if the space can be occupied when you return (though I think the effect is smaller than at first glance). All in all, it's nice to see what people can work out for themselves-- and remember, if the city government were effective at removing snow, this practice would not have evolved in the first place.
Why talk about it now? One municipality here, Dormont, has decided it's gone far enough. Starting today, anyone that leaves an item in the road will have that item removed.
It's government against social norms here in Pittsburgh! Situations like these generally don't have clean outcomes.