Arduino Basic + ATmega8 + ATtiny85 = Teach Class for Kids!

Here's the PS2 Mouse/Keyboard code:

http://www.arduino.cc/playground/ComponentLib/Ps2mouse

And here's how to use 2-wires to connect the LCD with a cheap shift-chip:

http://code.google.com/p/arduinoshiftreglcd/

Them there's also the ATtiny85 I2C/Uart code:

http://code.google.com/p/arduino-tiny/