Where to learn SQL Server Service Broker?
Some online articles:


An Introduction to SQL Server Service Broker
Service Broker Tutorials


I myself host a few articles:


Reusing Conversations
Writing Service Broker Procedures
Troubleshooting Conversations


And there are several introduction level practical examples:


Centralized Asynchronous Auditing with Service Broker
Service Broker Foundations Workbench
Using Service Broker instead of Replication
Introducing Distributed Messaging using Service Broker in SQL Server 2005
Building the MSDN Aggregation System