Sinead introduced me to a cool crowdsourcing game from the National Library of Finland called Digitalkoot. As your proof words from the OCRing of 19th century newspapers you create bridges for moles. The YouTube above shows the game. The company behind this will apparently build and run a game like this for you for a fee.
She also pointed me to Your Paintings Tagger which is a UK project to get 200,000 publically owned oil paintings tagged. The tagging is not just for the painting, but also for parts of the paintings.