"J for Haskell Programmers" - http://crypto.stanford.edu/~blynn/haskell/jfh.html
Talking about data analysis
"Data Analysis using J" - http://csilo.com/static/DataAnalysisWithJ.html
J for IPython - https://github.com/Synthetica9/JMagic, https://github.com/adrian17/jkernel
and there's https://www.reddit.com/r/apljk/