At the time of writing this, I believe these things take up most of my “mindspace” in some form or another:

• Data Mining: algorithms for making sense of vast amounts of data
• AI and Machine Learning: building systems that “learn” by themselves
• Psychology and philosophy of “learning” in humans
• Distributed computing: writing programs that harness the maximum potential of clusters of computers
• Economics, human motivations, and the structures and complexities of the globalized world
• Effective management, leadership, and how to get things done
• TED, Quora and crowdsourced knowledge
• Acoustic fingerstyle guitar: me encanta la guitarra Espanola :)