USA Today uses Zaplet to "e-mail this story"
I've asked Zaplet whether they intend to let everyone use such a feature. Sites such as Backflip, Recommend-it or Spyonit let you customize their service to put them on your site (gotta do it here sometime.) It's free advertising for them, and hopefully more stickiness/retention for content sites (if you leave me now, you'll take away the biggest part of me.)
08/04/01 update: they don't anymore, either because USA Today (or its readers) didn't like it, or more probably because Zaplet is now focused on the enterprise market.