Human Brain Cloud is a pretty amusing timewaster with a great visualisation interface, and lots of (untapped) potential for tagging applications.
HBC asks everyone online to ‘free associate’ with particular words which then have relationships built between them. Much like what we at the Powerhouse do when we data-mine search terms, HBC is building an enormous lexicon of word relationships – something that would have great potential if linked with tag databases. Whilst ESP Game and related projects are useful for connecting different words with images and forming ‘agreed’ descriptions, if this were to be coupled with multi-source, distributed, dynamic synonym generation then the number of words/tags would skyrocket, greatly increasing discoverability.
One warning – there is no censorship on the site at the moment, so be warned that some associations may not be appropriate or worksafe.