I just noticed this, but in the Terminal's File menu, there is a "New Command..." option. It may not seem too powerful, but the real beauty of it is the "Run command inside a shell" check box. If it is checked, the command will be executed in a new shell like this: $ [command you specified in the dialog] ; exit.
When the command has finished executing, you are dumped out of the shell. However, if the "Run command inside a shell" check box is left unchecked, the command you specify is run shell-less. It's great if you use a slow-to-launch shell (bash springs to mind :-) for launching a quick top or other command in a new window.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2003062021185119