InDesign CS3's Multi-file Place command makes short work of placing multiple files into your layout. But what if all the files you need aren't in the same folder? Here's how to place images from multiple folders at once with Multi-File Place:
On the Mac, use List view instead of Column view in the Place dialog box. (List view is the one with the "flippy triangles" that allow you to view the contents of multiple folders simultaneously). Then flip open the folders you need, and command-click to select multiple files.
On Windows, you will need to switch to the "Adobe Dialog" by clicking on the Use Adobe Dialog button in the bottom-left corner of the Place dialog box. Then, use the icon in the upper-right corner to switch to Details view. Now you can open multiple folders simultaneously by clicking on the plus signs to the left of the folder names, and then control-click to select multiple files.