If you use Saft, the Safari enhancer from Hao Li, you can add a Refresh shorcut to Saft's contextual menu (Saft also adds a very useful 'Back' button to the top of the contextual menu) In Safari Preferences, click on the Saft tab/icon and select the Shortcuts tab. Add a new shortcut named Refresh (put Refresh in both the Name and Shortcut fields). In the URL field, put:
javascript:window.location=self.location
It's probably debatable whether this is actually a Shortcut; but if you're a contextual menu user, this is a good stop gap until Safari picks up little features like this.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050213154457466