The BBC micro:bit is a very small (about half the size of a credit card), affordable ($16.50 for's Go bundle which includes the micro:bit, a cable, battery pack and batteries) codeable computer.
The online coding environment lets you program with a Microsoft Block Editor (very similar to Scratch), Python, Java, or C++.  The environment includes an image simulating the bit so that programs can be tested online before downloading to the micro:bit.

It's very easy to develop programs that let you control the LED array and the two buttons, creating scrolling text messages, images, and simple games.  The bit also has a motion detector and a compass. Sparkfun has put together a number of kits for extending the micro:bit including a weather station, robot car, and Inventor's Kit.  Sparkfun has also developed some excellent (as usual) video tutorials and guides for the bit.  Here's the link to the Go bundle and beginner's tutorial:

I think the micro:bit provides a great introduction to coding.  It's interactive - the LED array provides quick feedback - it's inexpensive, and it's easy to learn.