What language did the Buddha speak?

Do we know, or have a good idea, what language the historical Buddha (Siddhārtha Gautama) spoke. I've just assumed it is Pali but a moment's thought tells me this is probably wrong since the Pali canon was written hundreds of years after the Buddha died. If we know what language he spoke do we know if this language had a wide geographical area and if it is likely that he would have preached in this language or would he have used one more associated with religious practice.