Amazon Route 53 - Amazon Route 53 is a highly available and scalable DNS web service.
Nuage - Nuage provides domain naming services.
GoDaddy DNS - GoDaddy DNS helps manage website performance, reliability and security.
Brandpa - Domain names for startups
DNSimple - Domain Name Service with low cost hosted DNS, an easy to use web interface, and a REST API for automation. Hosting DNS has never been so simple.
DomainWatch - Domain Monitoring Made Easy