There's a new service called the Amazon Mechanical Turk. It lets you submit tasks to be performed by Amazon users.
Phil Wainewright describes the service in Fine-grained tail of the Mechanical Turk and Wetware as a service. Whereas Web services, and services in general, are supposed to be coarse-grained, Phil describes this as a rare example of fine-grained Web services. Apparently because the tasks often only take a few seconds to perform. I don't really get where that conclution comes from, but the Turk sounds interesting nevertheless.
I'm tempted to say that the Turk is just workflow. You decide on work categories or task types, then create a worklist for each. Then someone with a task to be performed adds it as a work item to the proper worklist. Someone wishing to perform a task selects an appropriate worklist, then acquires a work item from the worklist and performs it.
But can this be done as Web services? You'd need one for browsing and selecting a worklist, one for adding a work item, one for acquiring a work item, and one for receiving notification that your work item has been completed. Perhaps this is what the Turk does.
I'm not clear on why Amazon users are supposed to want to perform these tasks for free, but what the heck.
The Amazon Mechanical Turk: Workflow for Human Tasks