Barcode Scanner should ship with Android. It allows your device to scan most barcodes. Many applications actually rely on this software, for example, Key Ring. Barcodes? Who cares? I thought that at first too. What makes Barcode Scanner so useful is the proliferation of QR Codes, which are fancy square barcodes that allow encoding of many different type of data. For example, I have included a QR Codes in all my reviews. The QR Code contains an address to the Android Market allowing you to download the app within seconds. Just scan the code in (right from your monitor) and you will be prompted to download the app. No searching, no typing.
QR Codes also allow encoding of contact information, latitude and longitude, plain text, etc. My next set of business cards will have a QR Code containing my contact information allowing people to add me to their address books with the scan of a code. I also plan on using them in my geocaching activities.
Want to generate your own QR Code? Have at it.