Domainr - Domainr is the only ICANN-accredited domain status API provider.
NameQL - Fast and friendly way to find a usable name for your idea, app or business
Lean Domain Search - Find a Great Domain Name w/ twitter handle availability
Naminum - A company name generator that's actually useful
Instant Domain Search - Search domain names instantly by showing results as you type.
Naming Matters - A new, affordable naming startup for startups