Problem: We needed a way to see how many Planned Hours had been allocated to a Master Project's Sub Projects. We often get retainer engagements for 500 hours, so we create a Master Project with 500 planned hours. As we create Sub Projects underneath that master, we want to see where we're at with combined planned hours from Sub Projects. Again, easy to do with reports - but we don't want to have to look at reports to understand what is going on with a Project. We want to see everything on the Project's detail page.  

Solution: Create a rollup from the Project object to a field on the related Master Project called "Sub Project's Planned Hours." Send along the sum of the Planned Hours field on all child Sub Projects. Project Management FinancialForce