ZCash! It was recently released! http://coinmarketcap.com/currencies/zcash/
It also presented a new algo to mine with called Equihash which is memory focused and will be implemented by Steem as well after the hardfork!
I use one r9 390x GPU to mine with.
Could I mine on a macbook air?
You could practically mine it I think, but I doubt its recommended on a laptop.
Also not really sure about the OS, I use Windows and know there is some for Linux.
got it