[eluser]jakeone[/eluser]
The original question is a bit like saying, "Show me the houses built with hammer X". A framework is just a tool, you still need to write good PHP.
Far too many frameworks out there are behemoths that insist on you doing it "their way". Furthermore, the modules that are supposed to save you time end up costing you a lot more with their steep learning curves and having to occasionally hack around to make it do what you want it to do. For example, I abandoned Cake after three frustrating weeks (far too much "automagic" and poor documentation for my liking) and settled on CI because of its simplicity and ease of installation.
As for what "big" sites you can build with CI, I think you're only limited by how many big sites you can build with PHP.
