Petfinder.org has many dogs and puppies that need homes. While they are not necessarily free, they are desperate. Around here, they will show you the dogs in your local shelters and rescue agencies. Save a life, you will never be sorry. I'm so pleased that people who answered have supported pound puppies.
The best place to adopt any pet is your local ASPCA or Humane Society shelter. Will there be a charge? Most likely, yes. Our local Humane Society charges $55 for a dog. That may seem a lot of money, but they must feed and care for the animals in their shelter, and have to raise the money for it somehow. This is one way. And it's a lot less than a pet store or breeder will charge for a "pedigreed" pet. That isn't the only reason to adopt this way: as another poster stated, you'll be saving that pup's life in most cases. The saddest fact of life (and death) about American pet shelters is that there simply aren't enough people who care enough to adopt and care for a pet in a responsible way. Every year in this country, according to the best estimate of the Humane Society of the US, or HSUS, 6-8 MILLION cats and dogs are placed in shelters. Of those, 3-4 million are euthanized because they're not adopted. And I don't know about you, but I find those statistics horrifying and tragic. I am guardian to five cats--which is the legal limit I can have in my home in my municipality. I have no dogs, as neither I nor my husband can walk dogs as they should be walked on a regular basis. And, if we can't meet an animal's physical and emotional needs, we won't adopt them. Best estimates are that, to empty the shelters in this country and keep them empty, every man, woman, and child would have to adopt five cats and two dogs EACH. What's the answer to this problem? Neuter or spay your pets, without exception! And, if you have the time and energy, become a TNR facilitator. What does that mean? TNR means "Trap, Neuter, Return". In short, the TNRF traps feral cats and takes them to shelters. They are spayed or neutered, immunized, and one ear is cropped (that is, a bit of it is clipped off, so in future, TNRFs will be able to tell the cat has been neutered, and doesn't need to be trapped again. I consider TNRFs to be unsung heroes. I know a couple who each manage a couple of colonies of feral cats--they beg food for them, get them medical care if they're sick or injured, if possible rig up inexpensive but sturdy, simple shelters for them, and otherwise don't interfere with their lives. Of course, they'd love to be able to take all those poor kitties in and give them better lives, but to be frank, it's simply impossible. But God bless them for the work they do.