We don't often talk about advertising here, but this banner ad -- I won't tell you who it's for, as it will spoil the ending, but WorldChanging readers will appreciate the cause -- is simple, powerful, and an excellent use of interactive media. It's a "hangman" game in Flash: click on the letters to try to spell the phrase, and when you guess wrong, gallows are gradually built and a man is hanged (a rather morbid game, admittedly). Check it out.
Wow. It's rare that the interactive side of a piece so perfectly mimics the message. The race against time, the one by one writing of the letters, the life-saving importance what you are doing, the difficulty of figuring out what's happening behind a veil of secrecy-- these all perfectly reflect what you do as an Amnesty member. As an interactive designer, I'm really inspired by this example.