UNICEF really appeals to me. I have board member here at YFC Geneva that works for them. They work hard at empowering young people, and overall…they seem to just be about good things.
I found this article about how UNICEF is working to use Second Life in innovative ways to bring education and empowerment to adolescents (something they do well) about issues that really matter.
If you have some time, look around their site. If you have extra money, consider them as a place to give!