I don't think it's possible to find an example where pure, unadulterated socialism has "worked". I don't think there ever will be, either. But one can still find reasonable, individual socialist polices "working" rather well. The welfare state is a pretty socialist idea, for example, and we're long past the time where anyone is seriously going to argue against doing away with it - in its entirety, at least.
Maybe Socialism tends to fail because it sets impossible standards for success, and more fundamentally it's not in enough people's nature to be altruistic and selfless in the way that Socialism requires. But then again, Capitalism doesn't exactly "work" for most people either. But then since it doesn't purport to, people apparently tend to forgive its failures while lambasting socialism, or anything that even remotely resembles it.