This is a resource plan that I did many years ago when I was in the early stages of my career at Xerox. As you can see, it is handwritten on graph paper! Comments about age aside, I wanted to present this artifact to illustrate a principle about resource planning. I organized all of my people on the left hand side. I listed the projects they were working on and entered a forecast of the percent of their time dedicated to each project in each time period.
Believe it or not, this methodology for resource planning is still in use today -- even though people don't use graph paper. Instead, they do it in Excel. Despite the presence of high quality project management scheduling tools of all varieties, from simple to complex, many resource managers still manage their resource checkbook - their allocation of people to projects - with Excel.
Limitations of Excel
Excel works well in very small organizations; not so well when there are many resource and project managers involved. The problem of course is consolidation and consistency. This is why PDWare Portfolio has been designed with an MS Excel frontend and a SQL Server or Oracle backend.