DNS Web Service
Many people utilize the Amazon Web Services and now they have added a highly available and scalable Domain Name System named Amazon Route 53. Here is a quote from their release about the system.
Route 53 effectively connects user requests to infrastructure running in Amazon Web Services (AWS) — such as an Amazon Elastic Compute Cloud (Amazon EC2) instance, an Amazon Elastic Load Balancer, or an Amazon Simple Storage Service (Amazon S3) bucket — and can also be used to route users to infrastructure outside of AWS.
They have an easy-to-use self service API. You pay $1.00 per month and 50 cents per million queries for the first billion then 25 cents above that.