Some PIC MCU's can control a I2C bus. I2C is a two wired communication protocol between chips. EEPROMS, Input/Output extenders, temperature sensors and lots more can be used as slaves on the bus. Check this link for more information on the I2C bus.
Before using a PIC as master I wanted to know more about I2C.
With a breadboard filled with eight PCF8574P chips and LED arrays, I could control then with my Nintendo DS Lite and the DSBrut extension card.
It is also possible to control I2C chips via the serial port. A while ago I found Asgaut's site where a small drawing is shown of a RS232/I2C interface using four 2N7002 MOSFET's. (see picture below-left)
After creating the interface it would be nice to make the LED's flash in random sequences. Therefore I created a small VB6 program that controls all chips on the breadboard with a random output.
If you are interested in the program and the sources, get it here.