The Wellcome Foundation has commissioned an iOS and online browser game named Filth Fair to coincide with its Dirt season, which runs until August 31. Players must track down a series of words associated with dirt and disease, using cryptic clues to guess at the missing letters. Think of it as dirty hangman. No wait, don't think of that.
It's quite compelling, especially as, when you guess a word correctly you get a link to a relevant web article so you get to learn lots of interesting things about squalor and hygiene through the ages.