Tab Duplicator, A Safari 5 Extension
Tab Duplicator adds a contextual menu item as well as a toolbar icon1 that will duplicate your active tab. By default it creates a new tab in the background, but it can be configured to make them foreground as well. You can also select tab positioning (first, last, before active tab, after active tab).
Changes in 1.2
Added toolbar icon in addition to contextual menu. If you don't want it you can hold command and click and drag it off to remove.
You can now choose where to position your duplicated tabs. Choices are after current tab (default), before current tab, beginning, or end.
Optimized code. No more injected script.
Validation of events (disables button/contextual menu item if no URL is loaded)
Thanks to Brian Kim for the icon!