==> logic/smullyan/fork.two.men.s <==
The fact that there are two is a red herring - you only need one of 
either type.  You ask him the following question: "If I were to ask
you if the left fork leads to Someplaceorother, would you say 'yes'?"

If the person asked is a truthteller, he will answer "yes" if the left
fork leads to Someplaceorother, and "no" otherwise.  But so will the
liar.  So, either way, go left is the answer is "yes", and right otherwise.

It is possible, of course, that the liars are malicious, and they will tell
the truth if they figure out that you are trying to trick them.