There's an app for the iPhone called Photographer's Workflow. You set up a template with standard tasks, and when you create an event, it autopopulates your Google calendar with these tasks. For example, for a wedding, you might define a multitude of tasks for both before and after the actual date. If it worked with Toodledo (I've requested it), it would be perfect.
Toodledo's template feature has promise, but I'd really like for it to have the relative date feature. I'd like to be able to set a main due date, and have the sub-tasks due dates be relative to that date. For example, if I want a main due date of July 1, I'd like to be able to set sub-task due dates of 1 day prior, 5 days prior, 5 days after, etc. That way, I could duplicate the template for each job, set a main date, and have the sub-task due dates autopopulate.