Is China about to implode? Paul Krugman is worth a read on the subject, though in the end he doesn't know any better than anyone else. For what it's worth, the one encouraging thing I've consistently read about China is that their property bubble is largely driven by cash purchases, not debt. And non-debt bubbles, like the dotcom bubble, are inherently less destructive when they burst than debt-driven bubbles.
Of course, even a non-debt bubble can cause a lot of damage if it comes on top of an already fragile world economy — an economy that will be more fragile yet if Europe continues along its self-destructive path. It's sort of hard to believe that America might have the best managed large economy in the world, but you know what? We might.