Domainz.io - Premium domains, for not so premium prices
PowerDNS - PowerDNS offers open source DNS software, services, and support.
Park.io - The best place to backorder/drop purchase expiring ccTLD domain names.
dnsmasq - Dnsmasq is a lightweight, easy to configure DNS forwarder and DHCP server.
estibot - Domain name valuation
Unbound - Unbound is a validating, recursive, and caching DNS resolver.