http://www.greyhoundpets.org/ will help you find the greyhound organization in your area of the United States.
http://www.gpawisconsin.org/ is one of my favorite charities to donate to. We find homes for retired greyhounds in and around Wisconsin.
http://www.greyhoundcrossroads.com/ is a greyhound adoption group serving North and South Carolina.
http://www.casualbling.com/Hope_for_Hounds.html is raising money for cancer research in dogs.
The United Way raises money for needs in your community.