Ammonia isn't as popular as a cleaning agent as it could be because many people don't like the fumes. It's cheap and efficient when you have a tough cleaning job involving grease or unknown gunk, though, and since manufacturer's have added scents, ammonia isn't even quite as smelly.
Those famous fumes are the real gunk-loosening power of ammonia. To use them, put a small amount of ammonia in a container that can be closed - like your oven or a plastic bag. To minimize the use even more (and maximize your savings), put it in a shallow container like a pie pan (glass only) in the bottom rack of your oven, then put drip pans, electric skillets or anything else that's coated with grease or baked on gunk, in the oven. Close the oven door and leave it all there overnight. The gunk will be loosened by morning so a quick scrub will have everything, including the oven, shining.
It will also remove wax on floors, clean windows (very much diluted), woodwork and almost anything else.
At the price, you can't beat it's cleaning power, but it isn't as friendly as vinegar or baking soda, so keep it away from kids and pets and don't breathe any more fumes than you have to.