One Word Domains - Database of all available one-word domains
Domcomp - No-nonsense domain price comparisons, updated daily
Domainz.io - Premium domains, for not so premium prices
Pricepeek - Compare prices of the same product across all Amazon locales
Undeveloped - Domains you never thought were available
dofo.com - Domain search platform Dofo.com gathers all registered (350 million) domains of the world in a single place. Dofo also brings together all the domain names that are on sale, provides useful features, all completely free.