United States
1-877-Pet-Move (738-6683)
International
I came across a great new site today called Animaland, which is run by the ASPCA. It's designed for kids and young adults, helping them sort through the important issues of pet rescue, pet adoption and caring for animals humanely.
One part asks kids to write to their Congressmen and women to lobby for animal rights. Another section reminds kids of their own rights when it comes to dissecting animals in school, something that I remember very well from high school when I refused to dissect a fetal pig. They even have a great little question and answer section called "Ask Azula," which uses a fun mascot to answer questions about pets (ever wonder why you don't see baby pigeons? Ten year-old Naomi did!).
If you have any kiddos in the house, this is a great site to have them check out. And even if you're an adult, you might learn a thing or two!