MySQL - The world's most popular open source database
Google App Engine - A powerful platform to build web and mobile apps that scale automatically.
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
Salesforce Platform - Salesforce Platform is a comprehensive PaaS solution that paves the way for the developers to test, build, and mitigate the issues in the cloud application before the final deployment.
SQLite - SQLite Home Page
Heroku - Agile deployment platform for Ruby, Node.js, Clojure, Java, Python, and Scala. Setup takes only minutes and deploys are instant through git. Leave tedious server maintenance to Heroku and focus on your code.