Click the picture of the bay pony that says 'Save a Horse' and 'Click here once a Day' and has a horseshoe on it, and they will donate a cup of grain to Habitat for Horses.
Plus, if you browse thier site and order anything, they donate a certain of the proceeds to HfH as well. Just love these guys.
I also have a 'goodsearch' toolbar, I have had it for many years and had no problem with the download. Here is the site where you can get the download, and everytime you search the net, a small portion will go to the charity of your choice. Mine is set for USERL, the United States Equine Rescue League I work with outta Richmond, Virginia, but you have alot of choices, horses and other charities, you can search for.
GoodSearch : Support your favorite charity or school.
You can also use the link and search directly if you are uncomfortable with the idea of a download or a toolbar, but you hafta reset your charity every time I think. I have the download, and it has never given me a moment's grief.