Welcome
This WordPress blog is using Amazon Relational Database Service (Amazon RDS) instead of a local hosted MySQL database.
A WordPress MU demo is also available here. It uses Amazon RDS for its database. You are welcome to try it and create a blog for testing.
News
I have posted information and a tutorial on WordPress and Amazon RDS.
I see that someone is already looking for a coder to move his WordPress MU database to Amazon RDS.