Cloudflare are a CDN that specialise in DDOS protection, as part of this they will host your DNS. They have a free level service with minimal functionality, but you can delegate your DNS to them and they are excellent. I haven't had a tick of downtime across multiple domains in 2 years with them and the webui is easy to use. You get free analytics if you want to turn that on also. I use these guys for my top level DNS and then delegate subdomains to Amazon. The Amazon part costs me like 60p a month or something.