in reply to what do you use for job queuing?

If I understand the topic correctly, you might want to consider the "trivial" solution of setting up a dispatch table in a database and running monitoring scripts on each machine in the cluster. Each monitor-script would check for new work to process in the database, and update the dispatch table with "in-progress" and "completed" flags as need be. Of course this only works when the individual pieces can easily be broken apart, but I think this is often true for web-applications.