The Michelson and Morley experiment always seems to be the experiment that caused the dismissal of the aether and that lead to special relativity. I cannot see why this is, granted it contributed to these two points but in no more away then say the Fizeau experiments or experiments into stellar aberration. In fact, I think it was the contradiction between the results of these three experiments that lead to the dismal of the aether (as they thought of it at the time). So here is my question: Why is the Michelson and Morley experiment seen as the most important of these (and other experiments like them)? And how did this lead to the special theory of relativity?
The crucial thing to dismissal of the aether was not this experiment but the special relativity. There were alternative theories explaining the outcome of this experiment. The main base of the special relativity was not this experiment but Maxwell's theory of electromagnetism, from which it is a logical consequence. (And Maxwell's theory of magnetism was very well established, not only by experiments but by many practical applications.) But the experiment nicely confirms it, of course.
Michelson-Morley experiment, unlike the earlier experiments measures the speed of light with very high accuracy, due to the novel technology based on interference.