Hadoop As A Service (Infrastructure)

Amazon Elastic MapReduce

http://aws.amazon.com/elasticmapreduce/

BigInsights (IBM)

http://www-01.ibm.com/software/data/infosphere/biginsights/

GoGrid Big Data Solution

http://www.gogrid.com/solutions/big-data

Infochimps

http://www.infochimps.com/

Joyent Solution for Hadoop

http://joyent.com/products/joyent-cloud/features/hadoop

Mortar Data

http://www.mortardata.com/

Skytap

http://www.skytap.com/

Unified Analytics Service (Sungard)

VertiCloud

http://www.verticloud.com/

Windows Azure HD Insights (Microsoft)

https://www.hadooponazure.com/