Tool.Domains - Search free to register expired domains
BIND - BIND is by far the most widely used DNS software on the Internet.
Brandpa - Domain names for startups
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.