It was hard for me to decide what single product of Hinduism left the strongest impression on the most people. There are hindu concepts, such as karma and reincarnation that are so widespread that they became part of the English lexicon. However, concepts are not acts, and what I am looking for are the acts that are based in religious knowledge.
In my opinion, the greatest active influence of Hinduism in the modern world is the segregation and the oppression of the Pariahs, or Dalits, the caste of untouchables, which number some 200 million people. These people speak different languages, follow different religions (predominantly Hinduism, of course), live in different countries, but are oppressed just the same. The majority of Pariahs live in segregation and experience violence, murder and rape at the rate of hundreds of thousands registered cases a year. Although in India this mistreatment is on a slow decline, it is far from being anywhere near reasonable – more than half of the indian untouchables today live below poverty line and 62% are illiterate. The situation is even worse in Nepal, where no emancipation has yet taken place. Over 90% of the nepalese untouchables are illiterate and 80% live in poverty.
These are no small communities, Dalits constitute 20% of the population of Nepal and 16% of the population of India. There is no racial, ethnic, national, or even religious difference between a pariah and a member of a scheduled caste. The people in the region simply follow the laws attributed to the holy scriptures of Hinduism, the Indian caste system. It may have started as a simple merit-based classification but evolved into a rigid system of strictly segregated inherited social classes sometime around 3rd century CE. The system was officially abolished in India in 1950, but still plagues the society, deeply affecting the lives of hundreds of millions of people.