How do do "Facebook style" image tagging? I couldn't find a module that would allow "Facebook style" image tagging (select an area of an image and tag it with a username, for example).

Any good starting points to build such a feature?
It's called "image annotation" if you want to search for it.  There are a handful of modules, but not sure how great they work or how often they are maintained.  This one seemed the best:

http://drupal.org/project/image_annotate