I've been thinking about the Message Channel pattern lately.
In conversation, I tend to call a pipeline between apps a "channel," by which I assume it is (or will be implemented as) a Message Channel, for example a JMS Destination. Recently I've had to clarify that, especially in terms of "Is HTTP a channel?" That's lead me to think of four patterns, which I've started to document in Message Channel Revisited (on my wiki).
Message Channel Revisited