You do not really need a monitor and a keyboard for logging into the tiny credit card sized single board computer, the famous Raspberry Pi or RBPi; there are several ways to do that. One of the very simple ways is to listen in on two of the serial communication monitoring pins on the GPIO header of the RBPi.
Manufacturers of most computers have now given up on including serial ports on their products in favor of the more Universal Serial Bus or USB. However, connecting the serial pins on the RBPi to the USB port on the computer is not so straightforward. A special translator is required, one that understands and converts between the serial and USB protocols.
FTDI makes a special cable with an FT232 chip in between that can help to connect the serial port pins on the RBPi to the USB port of the computer and provide meaningful communication between the two. Modern Devices have gone one step further. Instead of having to deal with connectors or soldering on the RBPi side, they have designed a breakout board with the FT232 on it. The FT232 TTL signals are available on a header, which is suitable for plugging into the GPIO header on the RBPi; this is the USB BUB 1,
On one side of the BUB is an FTDI header, a six-pin version very common with most of the Arduino-compatible boards. The breakout area of the BUB is very handy as it allows you to reconfigure the signals to any of the pins on the second header. When you have to connect different devices such as the Parallax Propeller, this rerouting is very useful, as pinouts or the RBPi and the Parallax Propeller are different. The rerouting process also allows you to select the proper logic level (5V or 3.3V) for your device with a single jumper. You can suitably modify the breakout area of the BUB to enable it to connect appropriately to two different style devices without resoldering the connections.
When connecting to the RBPi, make sure you are connecting the Transmit of the RBPi to the Receive pin of the BUB, and the Transmit of the BUB to the Receive of the RBPi. Unless you follow this method of connections, BUB and RBPi will be unable to communicate with each other. For connecting with the RBPi, another very important thing to take care on the BUB is the logic level jumper. Make sure and double-check that it is connected to the 3.3V rail and NOT to the 5V.
Now that you have everything under control, boot up your RBPi, plug in the BUB and connect the other end of the serial cable to the USB port on your computer. All FTDI chips have a unique ID and this will show up as the device name. The device will be available under the /dev directory if you are using a Mac or Linux computer. On Linux, the BUB will show up as /dev/ttyUSBx, where x will depend on the number of USB devices already plugged in.