Gojko Adzic – Lazy web sites run faster:

"Clever choice of asynchronous processing is definitely one of the most important decisions in any enterprise system. This is especially true for Web sites, where it absolutely plays a key role. Here are a few ideas to think about when deciding how to split the work."

Also by Gojko Adzic – Messaging is not just for investment banks:

"A messaging solution might help to divide and conquer, isolating parts of the system so that they don’t really care about each other. It also makes the system easier to scale and extend. The agents can just publish requests to a message queue, not caring about who and where will actually process them. A number of different processes, running on different machines, can pick up requests and service them, pushing the results back to the message queue. The results might be delivered back to the original requester or picked up by another worker to continue or complete the job."