Programming a parallel port as digital I/O
With current technology, if you want to operate on a number of discrete I/O signals, your best bet is to tinker with a dedicated USB microcontroller, or a standard microcontroller coupled with an FTDI USB-to-232 interface. 

Old school parallel ports came in a variety of flavors, and not all could do input, since the port was primarily designed to send data to a printer. There were only a couple of handshaking lines that were actually dedicated to input. If you really want to use a USB parallel port, you should look for the EPP or ECP variants, as these were the bi-directional kind.