Someone turned me on to this yesterday. Lee Jeans Australia is running a very clever viral campaign. It's pretty involved [yet somehow very simple]:
Users that log on to a Lee Jeans Australia site are given the chance to expose a friend's secret. In a very simple and quick process [60 seconds], you upload a photo and write a short description of the friend's secret. The information is cleverly weaved in to a video template that is then uploaded to a seemingly real video blog site [complete with a message board, fake ads, etc.]. The exposee [if that's a word] is informed that their secret has been exposed via a very clever email that appears to have circulated for a while before reaching the exposee.
I made a video about myself to illustrate [with the character Kelly Leak, of Bad News Bears Fame, playing the role of my friend who has exposed my secret]. You can check it out by clicking here. Screenshots of video site and email below.