Though I like helping with any answers I can, I am found most often on StackOverflow. I particularly like helping debug and explain Guice, Dagger, and Mockito, which I count as some of the most-powerful (and sometimes least-intuitive) packages available in Java today.
My five favorite computer science inventions: Code-generating serialization layers (Protocol Buffers and Thrift), Bloom filters, Hilbert indexes, A* search, and CompactHashSet. I'm also a fan of DI and mocking frameworks, as you can see above. :)