Well, we are working on a project that provides Hive (and Hadoop Streaming) as a service. It's http://www.hadoopondemand.com and uses amazon ec2. We have just started our private beta and you are very welcome to join. And there is also amazon's offering EMR (http://aws.amazon.com/elasticmapreduce/) which also provides an interface to Hive and Pig.

EDIT: link to amazon's offering