Just before Christmas I invested in a PiRingo board which was a KickStarter Project. This is a small board which plugs directly into the Pi GPIO pins and it contains a ring of 12 Leds and two push buttons. There are a variety of led colours and configurations available. I chose the Christmas Wreath/Traffic Lights board which has 4 each of red green and yellow Leds. I bought this as an easy way to explore the I/O functions of the Raspberry Pi, and also as I wanted to use it with my eldest Grandson (aged 5) to get him interested in using the Pi.
The board is easy to put together with the aid of a soldering iron and some side cutters, and there are good construction details available on the PiRingo website. (The board is produced by 4tronix)
I developed a scratch program to show two different patterns of flashing Leds, which also used the two push buttons to select which pattern is displayed.
If you have a Pi and have not yet delved into the control side of things, then I can recommend this as a very convenient and cheap way to try things out.
A view of the program
The LEDS flashing
The program can be downloaded here