Good examples of object-oriented vs. procedural design

Question

I keep reading that object-oriented programming can basically be done in any programming language, and that in order to do so, explicit language support is not required. I.e. one can write object-oriented programs in, say, plain C.

What good examples of OO design using a procedural language are there, apart from GTK+?

Which open source projects are good examples of procedural design, on the other hand? (preferably C)

Answer 1

In C, OO programming usually takes the form of calling particular initialization and cleanup functions on struct pointers, and for polymorphism, passing around structs of function pointers. One example I can think of offhand is KVM.