I am an Apache Spark committer and PMC member working at Databricks, the company founded by the creators of Spark. I spend most of my time working on machine learning and graph processing on top of Spark. My current (open source) work can be found most easily by looking at:

Github for activity, especially within open source Apache Spark or Spark Packages
Databricks' Slideshare page or Spark Summit records for slides and talks
Databricks blog posts which I occasionally write