Advanced Job Scheduling?

Kagato asks: "I'm trying to make my company's Unix boxes more mission critical in the area of job scheduling. Scheduling jobs in Unix has been around since the dawn of time. On most systems you have 'cron' and 'at' to provide most of your scheduling needs. But outside the basic world of 'do this at such time' there are a slew of commercial products that handle dependencies, failure routes, monitoring, dependent notification, etc. Commercial products of this type have been around for years. Is there anything like this available in the GNU and Open Source worlds? I've been looking at Freshmeat, SourceForge and Google. I've found the pickings for advanced scheduling are pretty slim."