I visit Care2, regularly, both to click for donations and to send out e-cards.
I also visit
www.freedonation.com
You can click up to 20 times in each category: Stop AIDS, Promote Education, Support the Arts, Protect Environment, Defeat Cancer, House the Homeless, For the Children, and End Hunger.
It won the Best Charity Award Site from Yahoo in 2001.
In the end hunger category, each click provides a half cup of food to a hungry person.
In the for the children category, each click provides about 1/6 the cost of a dose of tuberculosis vaccine.
In the promote education category, each click provides one pencil to a child in a Third World country.
In the house the homeless category, each click provides 1.5 minutes of shelter for a homeless person.
I like this site because it's one-stop, loads quickly, and allows you to click 20 times in each category.