Water

Go Donate, seriously, its like $25. Thats not much considering. Its a small hand and gravity powered water purifier, which water is such a basic need but so rarely clean in a lot of areas. Clean water will make an excellent impact on any area. Plus you get some good karma, who doesn't want good karma?

Each system costs $25 and is good for 15,000 liters, which, we're told, is two years' worth of safe drinking water. Totally worth it. (via Good Magazine Blog

I know I'm going to donate a few the next paycheck I get.