The preference pane you're looking for is the Accounts pane. Once you're in there, make sure your user name is selected and then click on the Startup Items tab on the far right. You can drag and drop what you want to have open upon login.
The "open upon login" is the key reason (I believe) that the startup items moved to this preference pane with OS X, rather than keeping with the OS 9 Startup Items folder.
Hope this helps!
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