We already know that 3DS will include a WiiConnect24-like mode whereby users who carry their console around in sleep mode will still be able to interact with other consoles, exchanging information and downloading content anywhere they go. An interview with EA producer Ryan Stradling over at the Nintendo E3 Network seems to hint that the online aspects of the console will be more advanced than any Nintendo console yet seen.
Discussing an online friends list that will display, in real-time, what friends are playing, getting live updates including sports scores and even being able to share recent achievements with friends. It also sounds as though the 3DS will offer more robust communication services, with voice and text chat hinted at.
We've approached Nintendo for more information about these functions and will update you as soon as we know more. In the meantime, have a look at Ryan Stradler's interview over on the Nintendo E3 Network to hear it straight from the horse's mouth.