I recently picked up a nice little laser-cut case for my Arduino Due. This one is by GeauxRobot. They did a nice job on it including making little T-shaped button plastics to make the reset and erase buttons available.
This one does a nice job of supporting the ends of the board. All the I/O connectors are nice and flush with the top of the case so shields can be handled as well as the SPI and JTAG connectors being accessible.
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