This is a low-tech and low-cost project that you may find useful.
When testing an Arduino sketch, I often need some Leds, switches and potentiometers.
I have always them at hand with this hacked 170 points mini breadboard:
More info here
Neat idea, but I would have done it just a little differently.
I may even do this, as it could be handy... but a bit different setup though.
What I will do is:
1: Make an actual board for this.
2: Have a header on the board that plugs in, instead of soldering it.
3: Have several different boards for different situations, such as perhaps a bar-graph board, 7 segment board, etc.
I'll have some free time coming up, and I'll share it.
8)
Nice, I did something similar I few years ago.