Hi folks,
I wanted to let you know that I've created ProtoStax - stackable, modular enclosures for your prototyping. All ProtoStax enclosures can be stacked vertically and horizontally and work with each other (if you want to combine your Arduino with a breadboarded circuit, or an Arduino with a Raspberry Pi, for instance).
Our ProtoStax Enclosure for Arduino fits both Uno and Mega footprints.
The ProtoStax Enclosure for Breadboard/Custom boards fits a half-sized breadboard and has a USB cutout, making it suitable for any breadboard-friendly MCU like the Nano . (You can fit a full-sized breadboard by stacking two enclosures side-by-side)
All the cases have an internal clearance of 1.2 inches, giving you ample room for a Shield or two. You can start off with just the base platform for easy prototyping, and then quickly add the side walls and top for a finished enclosure. Extension kits allow you to add peripherals to your project/enclosure.
If you have other electronics that you are prototyping with, you can stack it with a ProtoStax Enclosure for Breadboard, or ProtoStax Enclosure for Raspberry Pi.
You can find out more about it here - https://www.protostax.com/
We also have a Project Hub with tutorials on different Arduino projects (and other projects) - just click on the "Project Hub" link from the navigation menu to be taken to the Hackster.io ProtoStax Project Hub. Projects are also available on the Arduino Project Hub, of course! 
Looking forward to your comments and feedback!
Thanks,
Sridhar Rajagopal