A Missing Pet
Provides a register of lost and found cats and dogs in the UK and also offers a free printable lost or found poster facility.
Nationwide register of lost dogs in the UK.
Found and Lost Pets
Posts details of lost and found dogs, cats, birds, rodents, horses and reptiles.
A completely free to use site that allows you to list your lost pet and search for pets found.
Lost Your Pet
Hosts found (free) and lost (for a fee) listings in the UK covering a wide variety of types of pet.
A large database of lost and found pets that have previously been a microchipped.
A UK organisation that works with police, veterinary practices and dog wardens to help find your lost or stolen pet. Includes registration details.