PowerDNS - PowerDNS offers open source DNS software, services, and support.
Domainz.io - Premium domains, for not so premium prices
dnsmasq - Dnsmasq is a lightweight, easy to configure DNS forwarder and DHCP server.
DomainWatch - Domain Monitoring Made Easy
Unbound - Unbound is a validating, recursive, and caching DNS resolver.
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.