Database as a Service DbaaS Product Directory

• Cloudant
• Database.com
• EnterpriseDB Postgres Plus Cloud Server
• FathomDB
• Heroku Postgres
• Kognitio
• MongoHQ / mongo machine
• mongolab (beta)
• NuoDB
• Quickbase
• RDS
• Redis To Go
• Scalebase
• ScaleDB
• SimpleDB
• SQLAzure
• Trackvia Cloud Database
• Vertica for the Cloud
• VMware vFabrid Data Director
• Xeround
• Younicycle
• ZeusDB

Source: Database as a Service DbaaS Product Directory « Database as a Service.