External links: Whether & how to distinguishing them from internal links, and to open them

How do other IAs/UXD's treat external links & what are the perceived pros/cons of different options. Specifically looking for recommendations on:

  • whether & how to visually distinguish external links from internal links
  • whether to open them in the same window/tab or a different window or tab

I've found some great feedback re these questions on http://www.ixda.org/search.php?tag=external+links & http://www.useit.com/alertbox/open_new_windows.html

Looking for additional opinions, thoughts & especially any usability test findings contributors of this site might have re these questions.

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