The TinyShield 16 Edge LEDs allows some cool and easy LED indications using only five I/O signals. The 16 LEDs are mounted around the outside of the board, and can easily be seen even when the LED board is in the middle of a TinyShield stackup. The LEDs are arranged using Charlieplexing, which is a technique to allow for control of multiple LEDs using fewer I/O signals. Available with Red, Green and Amber LED color options.
Tutorial here: TinyShield 16 Edge LEDs