When you have the key turned, is that rattling noise the same as when the car was working? You should hear the rumble of the engine firing. Try giving it some gas while turning the ignition. If the cylinders are firing, giving it gas should make it rumble louder and might help it start in cold weather.
If you can only hear the high rattle or whizzing of the starter motor, it is probably:
- bad starter (or connection to crankshaft)
- low voltage from battery
It's probably not the latter since you checked your battery recently. Google can help you check your starter.
Oh wait, you know what else it could be?
If your spark plugs aren't firing, the engine won't rumble either. So it could be your distributor or its connections. Try this: https://www.youtube.com/watch?v=mUOmsGiirTU
If you can get a hold of a diagnostics computer, it might help you.