I found these Arduino Uno clones (link) on Ali Express for £2.16 each with free shipping from china, I can’t even get Diavolino for that little (Also a Diavolino needs a RS232 / FTDI or something as well).

These clones come with something different, rather than the usual FTDI they come with a CH340G / CH341G Serial/USB chip.

Mac OSX doesn’t have the drivers by default (Windows 7 finds it in the driver database).

Download the driver

You should be able to get the driver from the Chinese company that developed it: here. It took forever to download, so I put up a copy Here – CH341SER_MAC.

Install it

1. Download the driver
2. unzip it
3. Open the folder
4. Run installer found in that folder
5. If asked to restart, do not restart just yet.
6. This next step is only needed if you are on OS-X Yosemite. possibly needs done on other versions:
   • Open Terminal Application, then run e this:
   • sudo nvram boot-args="kext-dev-mode=1"
7. Now restart your Mac

Not bad to let you use a £3 Arduino UNO clone!