Jigsawnz' Arduino Uno and Breadboard holder is a really lovely design.
The kobolds here at the lab recently started working on a project using a mini breadboard, and beseeched Lao Zheng to reforge Jigsawnz' original design into something that would be more appropriate for their grubby little clawed hands.
This caddy will hold an Uno (or a dusty old Duemilanove, if you've still got one of those kicking around the toolbox) and your standard 4.5cm x 3cm breadboards, like these.
Seej patient zero. Barbie Armor Designer, artist, worst programmer ever. Mostly illiterate, but has minimal competence in spoken Mandarin. Not real clear on Ohm's law.