I run a DNS hosting service (SlickDNS, www.slickdns.com) and have seen a spike in signups today as a direct result of the Zerigo DDOS attack.

I can't claim that SlickDNS is invulnerable to DDOS attack, but FWIW it does run tinydns name servers which have good performance and excellent security. So if you're impacted by the Zerigo outage, feel free to check out SlickDNS. There's a 30-day free trial with all plans and record updates are pushed through to all the name servers in under 5 seconds.