http://www.youtube.com/watch?v=Uh6erfE9HYE

Second part of the video explains Zerocash. Matthew Green said they will release it in May (I think it's in the video, if not, I will try and find a prooflink for it).

Here's the SNARK paper:

http://eprint.iacr.org/2013/507

And this is my effort to organize info about it: http://wiki.nxtcrypto.org/wiki/NxtCash