Visualize files and directories

I use a program called Disk Inventory X. It has served me well for quite a while. And it's free :)

http://www.derlien.com/assets/main.jpghttp://www.derlien.com/assets/main.jpg


If you don't mind working from the command line, the tree command does what you want. It's more or less standard on Linux and comes with Windows. I gather it's not installed by default on the Mac, but it's easy to obtain.