square waves different freq on different pins

Hi guys,
i want to use my Arduino to generate pulses of different frequencies,

I have seen the tone library

but I think it can generate only a tone on one pin at a time?

so here my question

  1. how to use one Arduino to drive multiple frequencies on different pins
  2. can i generate frequencies lower than 31HZ [minimum for tone lib?]

Thanks!

Look at this:
http://forum.arduino.cc/index.php?topic=179761.0