Revish and Machine Tags
I noted before the discussion on machine tags. Another example has come about with Revish, the book review community, pulling in images from Flickr that use the book:isbn=********** tag. An example page is Bulletproof Ajax. From their blog: There are only a few people using this at Flickr at the moment, but there are a lot of fun possibilities. If you've tried a recipe from a cookery book, knitted something from a pattern in a book, live near a real world location used in a book, or know an author - if you've taken photos of any of these things and put them on Flickr, why not add a machine tag with the ISBN of the book they relate to?