Finding the Source of a Odd Smell Inside?

I came home one day after my AC went out and my house smelled odd. It is getting cooler so we have just been running fans in the house until we can get the AC fixed. But one day I came home and there was a smell in the house that smelled like someone had burned food and tried to add spices to make it better. The smell wouldn't be unbearable if it wasn't so strong. It is stronger in a few areas of the house than others, but I can't find where it is coming from. Any ideas?