Various approaches to 'asynchronous browse refinement un-selecting'

Dan Klyn assembled a set of guided navigation UI widgets at his Wildly Appropriate blog back in January, introducing them by writing, “For a good long while now I’ve been meaning to create a spreadsheet or Flickr set or something which could serve as a systematic and comprehensive roundup of the UI widgets that folks have designed for use with systems where users can perform asynchronous browse refinement un-selecting.” It’s a useful overview of the various ways different interface designs solve these similar problems.