DAN.COM - DAN is on a mission to make unused domains accessible to all
One Word Domains - Database of all available one-word domains
dofo.com - Domain search platform Dofo.com gathers all registered (350 million) domains of the world in a single place. Dofo also brings together all the domain names that are on sale, provides useful features, all completely free.
Undeveloped - Domains you never thought were available
BrandBucket - The original marketplace for business names and creative domain names.
Domainz.io - Premium domains, for not so premium prices