As of today (well, I have to go to the bank tomorrow to initiate the monthly transfers) My wife and I are foster parents of a 7 year old girl in Sierra Leone.

The organization who takes care of this is SOS-Kinderdorpen (SOS-childrensvillages)

The organization builds villages for homeless kids to live in, organizes local schools, helps them learn a trade... There are currently over 100 such villages.
You can sponsor a single child for 30 euros per month, or support the village in general for 20 euros per month.

I have the girl's name and picture of course, and while I'd love to share those, I will not do so because of privacy concerns. This is something they placed some emphasis on, so I am going to play by the rules.
We recevied a file with information about her, and about the past and present situation in Sierra Leone, which is one of the poorest nations in the world despite being rich in diamonds and ores...

So now our family has 2 children and 1 foster child.
I feel that this way I can do something back for those who are not so fortunate to be born in the rich part of the world.
I am not so naive to think I can change the world, but this way I make a change for 1 person who needs it.