Idea Generation Methods is a new resource listing dozens of approaches to ideation. Ideo’s Method Cards package many of the same techniques. One of my favorites is "Country Music". It reminds back to a driving game we used to play, "guess that country lyric". Pass hours in the car by tuning in a country station and completing the verse without ever having heard the song.
Posted by Troy Young

Another useful tool along the same lines is the Eno/ Schmidt Oblique Strategies. Not so much for idea generation as nudges during a creative process. I’ve posted about it on our company blog – http://blog.mediacatalyst.com/ – with links to more info and apps for your desktop.