One Word Domains - Database of all available one-word domains
Handshake.org - Decentralized certificate authority and naming
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!
Tool.Domains - Search free to register expired domains
Domainr - Domainr
Lean Domain Search - Find a Great Domain Name w/ twitter handle availability