This site has a good example (though the scroll is done with JavaScript and I think just an anchor link would be fine), but I'm not sure if the entire concept is a good idea.
"Back to top" links aren't harmful per se, as long as you don't try to hide them from some users and not others. Attempting to give different sets of users different experiences is considered harmful.
Visitors would only need a "Back to top" link if there is no additional navigation at the bottom of the page. Since I'm using a "fat footer" design, this link isn't necessary. The example site I linked above does not have any navigation in the footer, which is why the "Back to top" is a good idea.
Since I'm keeping the fat footer design, the "Back to top" link isn't needed.
This site has a good example (though the scroll is done with JavaScript and I think just an anchor link would be fine), but I'm not sure if the entire concept is a good idea.