I recently started with the Teensy 3.1, plus a Wiz820io Ethernet module.
Full sourcecode available for download.
My ArduServer software ported across without great drama. Once it was in the Teensy, I able to do much more than I achieved a while back, with a small Arduino and W5100.
From anywhere on the web, if you go to…
… a page opens with two buttons: “LED On” and “LED Off”. Clcik either, and an LED attached to the Teensy on my desk here changes state. (You could, of course, use the signal to do other things).
The LED shines on a light sensor. The webpage you are looking at tells you what the light sensor is seeing… so you know the LED has changed state, and as an example of how to read sensors from afar.
“Frills”: The Teensy also has a sensor checking the ambient light in the room, and a temperature sensor. The readings of both are also displayed on the webpage served up by the Teensy.
Full details, including sourcecode at…
… in the Arduserver3 section, which you can skip down to with…