I came across these two videos earlier this evening on the visual effects that were used in TF3. Here's a better description:
ILM and Digital Domain have both released videos breaking down all the work that went into the action you saw on screen. You might be surprised to find out that Optimus Prime, Autobots and Decpticons weren’t the only CG additions in the film. Whole real-world environments and complete shots were created within the computer – buildings, vehicles, bridges, skyscrapers, cities and planets.