The Giving What We Can Donor Lottery is a novel way to donate. Instead of simply donating to a particular charity (or to one of the EA funds), you make a donation into a very large pot of money, for a chance to win the right to donate the whole pot.
Your chance of winning is proportional to the size of your donation. So, if the pot was worth $100,000, and you entered with at $1,000 donation, you would have a 1% chance of winning.
Giving What We Can runs the donor lottery at least once a year, typically around the December Giving Season. Past winners have granted more than half a million dollars to projects that they thought would have the greatest chance of having a positive impact.