Bloody addictive mobile phone games!
No sooner have I weaned myself off Scrabble and Countdown, then I download Wordbrain... and, by Jimminy Cricket, it is bloody addictive.
It's essentially a wordfinder where the letters forming the identified linked words drop away from a grid once you have found the word. The depleted grid then offers new possibilities. Clear one 4x4 or 5x5 grid, then start another.
I currently have the brain of a whale according to the game's rating system. This is probably not a compliment...