It is taken to be an established fact of life that there are developed countries and developing countries, and that in this latter life is exceedingly hard.
Happily, there are many charities which are dedicated to addressing this imbalance. However, in the cases where there are multiple charities tackling particular problems, it can be difficult to know which charity to give to.
It is partly to inform people on this issue that the organisation Giving What We Can was founded. On their website you can find details of the most cost-effective charities, the analysis they use to come to their conclusions, and articles on donating to charity. You can also find information about the Pledge to Give - members of the organisation pledge to give at least 10% of their income (1% of their yearly expenditure if students or unemployed) to the most cost-effective charity they choose.
It is to be hoped that by doing this you can make a real difference to the terrible inequality which exists in the world.