How long does it take for electrical impulses from neurons to travel in the human brain? Consider the maximal distance between two separated areas in the human brain. How fast can information via neuronal excitement travel between these two locations?
This is hard to say because not as many studies measuring this in humans have been done as have been done in other primates, like macaque monkeys, and when it is done, it is usually done in patients who have some brain issue like epilepsy and have recording electrodes implanted for preparation for a procedure, and so may not have a typical response. Also it is hard to know how best to satisfy your requirement "the maximal distance between two separated areas in the human brain". 

That said, here's my attempt: about 25 to 30 ms. I get this from two sources:

1) a 1983 paper using epileptic patients with microwire electrodes in their brain at various regions. I pick the data of measurements of the visual response arriving in the occipital lobe because--thinking simply--it is at the back of the head on the other side of the head from the eyes, and so the "maximal distance" is the entire front-to-back length of the brain (the pathway being retina -> thalamus -> V1 of visual cortex). From the paper (page 490, bottom):


  Occipital Lobe Units: Using diffuse flash stimuli...the shortest
  latency of the 11 responsive occipital cortex cells was 31 ms; the
  mean latency was 63.6 ms (range, 31 to 110 ms, SD, 25.1).


2) A 2009 paper, also using epileptic patients which found, among other things:


  the evoked potential started ~20 ms earlier in V1 (25
  ms after stimulus onset;