The resource chart in Microsoft Project is a useful way of seeing how the resources on your project are loaded, but by default it only shows one resource at a time. This is not adequate when you want to see how the project as a whole is resourced. Unfortunately, the method to set it to show all resources is not easy to discover. In fact I'd been using Project for a couple of years before someone showed me how to do it (Thanks Adrian!). So to make things a little easier, here is how to show more than one resource in the resource graph view.
From the window menu select "split"
Select the top pane by clicking in it somewhere. You know it is selected because the bar on the far left containing the name of the view turns darker.
Go to the view menu and select any view which has resources - task usage, resource usage and the resource sheet are probably the most useful.
Select the bottom pane by clicking on it somewhere.
Go to the view menu and select the resource graph view.
Right click on the resource graph area on the right.
From the menu that pops up choose "Format Barstyles"
On the left half of the dialog box that appears (the part marked "Selected Resources") set the "Show as:" to be anything other than "Don't Show".
Click OK until you are back to where you started.
Now select resources or tasks with resources in the top pane and the chart for all of those selected resources will be shown in the bottom pane.
This tip works for Project 98, 2000, 2002, 2003 and likely future versions.