A paper by Orhan Firat, me and Yoshua Bengio on multi-way, multilingual neural machine translation is sadly but also happily a best paper runner up at NAACL’16. You can find the paper at
https://arxiv.org/abs/1601.01073
The code has also been made public recently by Orhan at
https://github.com/nyu-dl/dl4mt-multi