Lean Domain Search - Find a Great Domain Name w/ twitter handle availability
BrandBucket - The original marketplace for business names and creative domain names.
Panabee - Best way to search domain names, esp for apps and startups
Brandroot - Great Names for Great Ideas
Mashword - Find a name and register a domain for your business, baby, project, and more. Mashword is a powerful company and human name generator that determines the pronunciations of entered words and then creates unique combinations and variations.
Zlipa - Startup names with available dotcoms and logos