YAAH (yet another arduino holder)

thingiverse

This is an extra handy base for the Arduino Uno. It's perfect to keep a tiny breadboard nearby, with all its pins at your fingertips. Print it however you like. In case you need a compact solution for holding a microcontroller board, this design fits the bill. Its minimalist shape makes it easy to fit into tight spaces, and the detailed print gives you a clear view of every connection point.