You can find a lot more about changes to the Dock in Leopard elsewhere on the web. I just want to mention something I found and did. I wanted to group my Microsoft Office applications together in a “Stack.” Stacks are mentioned on Apple’s site, and a Stack is what is springing up in this picture:

Leopard will not let you just select a group of files and make a Stack from them. You can only make a Stack from a directory (folder). So, to get Word, Excel, and Powerpoint into one Stack I did the following.

1. I created a directory under /Applications/Microsoft Office 2004 I called OfficeApps.
2. I selected the three applications, did a Make Alias for each (right mouse button when selected), and moved the aliases into the new folder.
   
3. I then dragged the folder to the right side of the Dock.
   

Now, when I click on the Stack, I can click and select the application.