AWS resources
Many Hadoop technologies can be deployed on AWS as part of a self-managed cluster. But just as Amazon offers support for Elastic MapReduce, which handles Hadoop as a managed service, there are a few other services that are worth mentioning.
HBase on EMR
This isn't really a distinct service per se, but just as EMR has native support for Hive and Pig, it also now offers direct support for HBase clusters. This is a relatively new capability, and it will be interesting to see how well it works in practice; HBase has historically been quite sensitive to the quality of the network and system load.
SimpleDB
Amazon SimpleDB (http://aws.amazon.com/simpledb) is a service offering an HBase-like data model. This isn't actually implemented atop Hadoop, but we'll mention this and the following service as they do provide hosted alternatives worth considering if a HBase-like data model is of interest. The service has been around for several years and is very mature with well understood use cases...