The International Rescue Committee, founded in 1933, responds to humanitarian crises and helps refugees and other people affected by conflict and disaster survive and rebuild their lives. 86 cents of every dollar spent worldwide goes directly to programmes. IRC was originally founded at the suggestion of Albert Einstein to help people fleeing Nazi Germany.
Founded back in 1933, IRC has been doing this longer than most organisations on this list — the 86-cents-per-dollar figure is also worth weighing if programme efficiency matters to your choice. It's also worth knowing the organisation's origin: it was founded at Albert Einstein's suggestion to help people fleeing Nazi Germany, which gives its near-century of work a specific historical starting point.