If you're operating without too much space, travel with your Arduino a lot or just like to keep things neat and tidy then the following idea by Instructables user churchjw fits the bill. They have demonstrated how to use old VHS-format video cassette containers as portable Arduino workstations. A small piece of acrylic or wood can be mounted inside the case, of which two solderless breadboards can be attached and of course the Arduino board. For the idea travel setup, perhaps add a lipo battery and you can experiment with a laptop computer during travel (well, some of us do...) or when away from the bench.
It's a neat project and the enclosures can still be found at various thrift shops, and wouldn't cost much at all. For more information check out the Instructable page. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
On the topic of portable projects, if you're looking for a way of providing a USB-style 5V power supply from lower voltages such as those that can be found from rechargeable batteries or packs of AA cells then check out our USBboost module. It can generate 5V from anywhere between 1.2 and 4.5V, and offer a full 500 mA of current from supply voltages above 2.4V. Plus it has preset low-battery levels you can select with logic output to tell your project when the device should power-down - and of course it can power an iPod. So for more information and to order, check out the USBboost page.