The cook-top specific stuff that the previous owners left at my house is just a concoction of citric acid and detergent. After three years I'm still on that original container, a little goes a long way!

I use plain crystalline citric acid for all kinds of cleaning applications. You can get it in 2-4 lb. packages at stores that have beer-making supplies, in the canning department of grocery stores, or in the bulk department of some natural food stores.

Another thing that works really well with baked-on grease is one of those high pressure steam cleaners. Naturally I busted the nozzle on mine and haven't got a new one... but it worked really well for a while