http://www.lostdogsuk.com/

http://www.doglost.co.uk/

Please add a link to any other sites you know of.

http://www.lostlabs.com/

http://www.missingpet.net/

http://www.petsearchuk.org.uk/

http://www.petfinderonline.co.uk/

http://www.lostpetsos.org/reg.php

lost and found site for west midlands
http://www.k9searchuk.com/pound1.htm

dedicated to helping lost and found dogs, and dogs in need

www.alfieslostdogs.com

Mark can you please edit your post? It's http://www.doglost.co.uk    - no S

National Lost and Found Site with automatic matching facility
Working with animal welfares and individual listings

www.petslocated.com

www.animalfinders.co.uk is another site for lost pets - they notify all surrounding vets, council wardens and animal charities of missing pet. Also, make posters for printing out and above all is a FREE service. Really helpful site!