Quite some time ago, I acquired an old, rigid steel mountain bike that I planned to turn into a single speed. The bike sat in the storage closet for more than a year before I finally got around to buying the simple parts needed to run just one gear. 
 
The biggest reason I finally got around to it was that I hadn't ridden my road bike for more than two months and I needed something new to get me back on the bike. The single speed has certainly done the trick. 
 

QR code

I first learned of QR codes from a colleague who spent time in Japan. These little bar codes are fairly ubiquitous in Japan.

QR codes are square barcodes in which you can embed text Web links, SMS messages or phone numbers. Using a camera phone, you can snap a photo of the QR code and special software will decode the hidden message.