Nintendo has released the long-awaited 3DS firmware update that includes a free internet browser, tool for transferring DSiWare games to your 3DS, and access to the eShop. You can download the new firmware by going into the 3DS System Settings menu then choosing System Update.
The eShop opens with some vintage Game Boy games such as Super Mario Land, Alleyway, and Radar Mission (if you're in Europe, you get Tennis instead of Radar Mission). There are also a few freebies like Pokédex 3D and Excitebike 3D available though Excitebike 3D is only free until July 7.
Minor note about this firmware: there's an issue that causes Ridge Racer 3D to freeze when you press the B button at the Race Selection and Machine Selection screens. Nintendo will release another firmware update later in June to fix the freeze problem.