Brandpa - Domain names for startups
BrandHunt V2 - Search/track domain & social media handles in real time.
DomainWatch - Domain Monitoring Made Easy
Lean Domain Search - Find a Great Domain Name w/ twitter handle availability
Nuage - Nuage provides domain naming services.
NameMing - Get smart domain name suggestions using synonyms, suffixes, prefixes, short url, new gtlds to find the perfect domain name. Generate ideas for social user names and check availability for free!