All 3DS models can hypothetically support Amiibo, Nintendo's toys-to-life figurines. For now, though, only the New 3DS models with NFC tech built-in can use the toys without any extra hardware; Nintendo promises a wireless dongle--similar to Skylanders portals--will be released for older 3DS models sometime later this year.
All of this is moot, however, without a software update to enable Amiibo functionality. According to Nintendolife, that update to enable Amiibo in Super Smash Bros is coming tomorrow. This is curious timing for a couple of reasons. It lets New 3DS owners start using Amiibo in territories where the New 3DS has already been released--Japan, Australia and New Zealand. However the New 3DS doesn't drop until Friday in American and Europe, so if you want to use Amiibo out of the box, you'll have another firmware update to pull down on Friday after you procure your shiny New 3DS.
As for owners of older 3DS models? Well, I guess you'll have to wait until Nintendo releases that little portal. But it's nice to know the software will be ready to go, right?
Source: Nintendolife