Editor: The “New Tab” button is now a reality. There have been many 3rd Party Apps that add the tab button but also a lot of other stuff, too. This will only replace your existing “Add Bookmark” button in Safari for 10.5.X Leopard, with my “New Tab” button and the option of having “New Tabs” open with your HomePage. Nothing else, it’s simple and small. If you like your “Add Bookmark” button in Safari, sorry. I find, I make many more tabs than bookmarks and I could not change the picture on the button so, it was the only one that still made sense when thinking, New Tab.
You might want to backup your safari first, just in case Apple changes something and doesn't tell. This is easy, just make a copy somewhere, like in Documents or something.
Assuming your Original Safari is installed in your applications folder, Run the installer, the correct files will be replaced by mine, Safari, will Start or ReStart & Now you now have a “New Tab” button. Apply it by going to: View - Customize Toolbar... Drag the button to your toolbar like any other. The Homepage option is located in Preferences.
Don’t like it? Run the uninstaller I have provided or Delete your Safari from the Applications folder and drag your backup copy back in. Your bookmarks will be fine. Back to no “New Tab” Safari.