Particle Photon

I really like the Particle Photon. It's an inexpensive ($ 20) cloud-based hardware device. It has a lot of I/O pins, including both digitial and analog inputs and output, and works mostly like the Arduino, except it has built-in Wi-Fi and cloud support.

I'll occasionally post things to this site that can be useful when working with the Photon, but for now, here's a handy table of the I/O pins and what you can use each of them for. For example, which pins can be used for a tone output, and which ones can trigger an interrupt.
Particle Photon Pin Information Page