DAN.COM - DAN is on a mission to make unused domains accessible to all
Brandpa - Domain names for startups
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.
Lean Domain Search - Find a Great Domain Name w/ twitter handle availability
BrandBucket - The original marketplace for business names and creative domain names.
Domainr - Domainr is the only ICANN-accredited domain status API provider.