Microsoft have released a whitepaper on

Architecting SQL Server 2005 Service Broker Applications
. The whitepaper
focuses on when its appropriate to use Service Broker, design aspects for
message flow and processing, availability, and infrastructure.

I think its an excellent view of Service Broker implementation from a
medium-high level, with discussion of the methods used, without going in the
fine points of “how to”. Its an great read for dbas/developers/architects and
helps readers have a better understanding of both the design theory and basics
of Service Broker applications.

If you are trying to get your head around Service Broker and are finding
books-online to be a bit of a hard read,

this whitepaper
will really help.