Matt, AKA YouTube user MattsAwesomeStuff, has three video tutorials describing how he hacks broken microwave ovens in order to harvest transformers from the junk. The first video (embedded above) shows the complete disassembly of an oven using only a screwdriver, pliers, and hammer. Part two delves into the science of how the transformer works, while the third part shows how to wind your own transformer. Matt put a ton of work into these tutorials and it really shows!
How to Salvage Transformers From Dead Microwaves