I personally don't like to use File -> New Tab, right click and select New Tab or Command-T to open a new tab. I prefer one click of a button to open a new tab. If you don't use the Home button you can use it to open a new tab (you'll need to have the Dev Tools installed, too).
First, back up Safari. Then control-click on Safari, select Show Package Contents. Open Contents -> Resources -> English.lproj -> Browser.nib in Interface Builder. Click on the third button from the left in the browser window. Press Command-Shift-I. In the NSButton Info window that opens, select Connections from the pulldown menu. Click on "target" under Source, then click the Disconnect button. Select "newTab" from the list of Actions and click the Connect button. Save and close.
Now the Home button will open a new tab.
[robg adds: I haven't tried this one myself; command-T is my preferred method of adding a new tab.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030731130432566