Mour Powa!

One thing you need for just about every project is power.
Different voltages, different currents.
It can all get a bit messy. I have known about using computer power supplies as said source of said power, but these new(ish) boards make it a lot simpler.

I really really like this new version and will probably pick up two of them once they become available.

http://dangerousprototypes.com/2014/11/10/building-a-better-breakout-board-for-atx-psus/

Its important to note that the link at the bottom is for the old version, not this new USB version, so the price and features are very different.
(Like I said, I have held off getting one because I really wanted USB which the new one has two of).