I hear about his impact in Egypt, Persia, and Middle East regularly, but I'm having trouble finding any sources (which is understandable) about Alexander's time in India, and the Indus River Valley outside of the Battle of Hydaspes. After reading N.G.L. Hammond's book "The Genius of Alexander the Great" I have a little better understanding, but socially, and culturally did Alexander have that large of an impact in the Indian subcontinent?
Alexander did not stay in India too long to leave an impact. He defeated the king Porus and won area around the Jhelum river which is modern day Pakistan. His army refused to move deep into India and wanted to go back. Alexander left Seleucus to rule the area and turned back. There was no major impact on the indian history as such because later Seleucus was defeated by Chandra Gupta Maurya whose grand son Ashoka then ruled most of India and propagated Buddhism.