The add this widget is a lightweight and customizable tool that will help you bookmark every TUAW post websites to some of your favorite social bookmarking and news sites (I think it might also be the smallest widget ever, too). Upon installing, you need to chose a background color and one of three social services (with more on the way): del.icio.us, digg or Shadows. It currently only works with Safari (with more browsers also on the way), but it unfortunately doesn't pass any selected text to the bookmark submission (like many of the available bookmarklets), so I hope that's on the todo list as well.
For now, add this shows a lot of promise, and it's probably one of the handiest and out-of-your-way tools for getting your social groove on. Grab it over at DashboardWidgets.