Just a quick note for Arduino developers who have upgraded to Lion or Mountain Lion. Despite tools like the FTDI Friend claiming they don't need drivers, they do... as of Lion; but since they didn't when they came out we all got spoiled.
So, today I pulled an Adrweeny and a FTDI Friend out of the drawer to scale down a project I had been developing on an Uno, and found that the Arduino IDE couldn't talk to the rig. The serial port wasn't even available. A few minutes of googling, a few false starts, and I have it working.
So, if you are looking for instructions on programming an Arduino or Ardweeny with a FTDI Friend on Lion or Mountain Lion, it's as easy as this:
Or you can skip the writeup and jump to the latest driver version here: http://www.ftdichip.com/Drivers/VCP.htm
As an additional note, the above listed drives are also needed if you want to program a Seeeduino on Mountain Lion. Found that out while out in the Black Rock Desert for Burning Man and needed to reprogram my hat. (Another story... Coming soon.)