The TFwiki page of all three movies has been updated with huge information about the changes that were made before, during and after the production of the movies. It's a long but very interesting read. Enjoy!

Transformers:
http://tfwiki.net/wiki/Transformers_...ter_production

Transformers: ROTF
http://tfwiki.net/wiki/Revenge_of_th...ter_production

Transformers: DOTM
http://tfwiki.net/wiki/Transformers:...ter_production


Special thanks to eagc7 for the links.