I like gadgets. Some of the coolest gadgets are add-on boards like the Freescale board that works with the Win7 Sensor and Location API. Recently, Arduino and Netduino caught my eye. Arduino is an open source hardware platform / microcontroller with a long history. The specification for the board is completely open, allowing anyone to build one themselves, or purchase a pre-built one. Coding is typically done in C++. Tons of projects have been built on it over the years.
More about license, specs, what can you do with it on his blog post.