In a recent post Persistent Systems introduced CloudNinja for Java -- a multi-tenant reference application designed to help the Java community develop Java applications for Windows Azure. It is available at github.
This application is built on several common OSS libraries, such as:
The CloudNinja for Java application encompasses following features and functionalities:
Tenant-level customization (for example, managing logos)
Per-tenant data isolation
Providing support for log-in via different identity providers (for example, Yahoo!, Google, Windows Live ID)
General purpose task scheduler
For more detail, read the post here.