Ideally what you want is called a
DisplayPort Multi-Stream Transport Hub (MST), which effectively allows you to multiplex multiple monitors over a single DisplayPort connection. The problem is that MST hubs have been long on promises and short on availability, and even after 2 years they still haven't hit the market. If your goal is to drive two random monitors over a single DisplayPort connection, then this will be your only option.
In lieu of that, a handful of monitors support daisy chaining, which is what Apple is doing. This works, but of course it requires a monitor supports this functionality. Along with the Thunderbolt display, only a handful of monitors support this kind of functionality. The only non-Apple 27" monitor I'm aware of that supports this functionality though is Dell's latest monitor, the
U2713H.