Undergraduate mathematics, Statistics, Machine Learning, Intro to Apache Spark, Intro to Cloud Computing with Amazon

Physics, quantum mechanics, related math concepts like linear algebra, abstract vector spaces, differential equations, calculus.

Much of the material in the LW sequences.

Optimization and machine learning. Also, shell scripting, python, perl, matlab, computability, numerical methods, basic data structures and algorithms.

More randomly: electrochemical energy storage, Li-ion batteries, distance running, dog training, Christian theology, Latin, English/American literature, poetry.

Perhaps more people would sign up if 'teaching' was relaxed into 'guided discussion'? In that case, for example, the vegetarians could hang out together in Skype or just download instructions/videoes, each teaching the others some new dish to make their cooking more robust? I would then brew some vegetarian borsch (although it isn't supposed to be so).

Also, there is a difference between teaching a skill and teaching information. I could, for example, help people study Russian and Ukrainian, though I have never taught language before.