The most comprehensive site for finding worthy causes is idealist.org. They list thousands of non-profits working all over the country on everything from social justice to solar power. I also list a few ideas below.
If you’re worried about health care in America, check out these organizations:
The Patient Advocate Association
If you would like to find a non-profit community health center in your area, look at the
National Association of Community Health Centers
If you wish someone was doing something about the energy crisis, climate change, and the environment, give some money to