What are the Four Noble Truths? What are they?  Where are they found in the literature?  Are there any significant differences in them among the traditions?
Here is a version from the Triratna site


All existence is dukkha 
The cause of dukkha is craving 
The cessation of dukkha comes with the cessation of craving 
There is a path that leads from dukkha - (The path most commonly associated with this is the eightfold path).


Dukkha is commonly translated as suffering but the translation that I find more useful is unsatisfactoriness. The original meaning comes from an ill fitting chariot wheel. A bumpy ride if you will. 

The formulation is related to a medical diagnosis e.g.


The illness
The etiology (cause)
The prognosis
The cure


As far as I am aware the 4 Noble Truths are a central teaching in Buddhism perhaps comparable to the divinity of Christ for Christian's (controversial comparison maybe). I have not heard of any significant variations. I would be very interested to hear if they were any.