A new exploit has emerged which allows the Nintendo 3DS to play games from any region without the need for a flashcard or any software-based exploit.
RegionThree merely requires an SD card and access to the internet, and has been tested on the latest version of the 3DS firmware. The catch is that it doesn't work on the shiny New Nintendo 3DS, so you'll need to have a 3DS, 3DS XL or 2DS to take advantage of this exploit.
The video below shows the exploit in action:
The 3DS is the first portable system produced by Nintendo that features region locking. Region locking was a common practice in previous hardware generations, but both Sony and Microsoft have abandoned it with their latest systems.
It's very likely that Nintendo will patch this exploit in a future firmware update, but the time being, it's open season on importing.
Thanks to Eiffel65 for the tip!