Anti-RFID
You probably already heard about this easy idea to stop RFID from sending information. It reminds me to a print advertising, showing that the US spent millions to produce a ball-pen that works in space, while the USSR simple bought a pencil.
However, it's just that easy to avoid privacy issues with RFID. I found the best blog-entry in my neighborhood. Anita wrotes everything about it and even emailed the inventer Mark: "You might wonder why I would go out of my way to put RF sheilds in my pants, and then injecting RFID tags into myself and others. My philosphy is that there is nothing we can do at this point to prevent RFID from becoming pervasive. Understanding RFID's weaknesses before it becomes completely mainstream can be of great value to all of us."
We make Money not Art has a nice instructional video too.