NameCheckup - Find available social media username and domain for your startup, business, personal brand.
Namewink - Get brand name ideas and domain name suggestions for your startup, business, company or side-project.
Instant Domain Search - Search domain names instantly by showing results as you type.
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
TMchecks - TMchecks is a free and easy to use trade mark searching tool.