Rackspace lets you manage your DNS using their Cloud Control Panel and API to list, add, modify, and remove domains, subdomains, and records, as well as import and export domains and records. This service is included free with every cloud account. Globally positioned and load balanced, their DNS servers employ a user-friendly interface, powerful RESTful API, and easy migrations.
CloudFlare is a powerful content delivery network. When you start using CloudFlare, your site becomes part of the CloudFlare network. This network routes your web site traffic through CloudFlare's global network of dataDNS Management Tools Cloudflare