Cyber Familator Lite Adapter Plays Famicom Cartridges on DS
This fantastic bit of hardware called the "CYBER Familator Lite" is an adapter that lets you plug Famicom cartridges directly into the unit to be played on your Nintendo DS. (The "Famicom" was known as the NES here in the States.)
If I'm not mistaken, the pin layout on Famicom carts was different than NES carts, so this one probably won't work with North American hardware. Too bad, because it's clunky in just the right way.
Product Page (Japanese) [CyberGadget.jp via Kotaku via DS Fanboy]

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Back in the day, there was an adaptor called "the Bridge" that allowed you to play Famicon games on the NES. It's possible there was an adaptor that did the reverse. Of course I think we finally got rid of our last Famicon/NES cartidges last year, otherwise I'd be tracking this down right now!
If you can find an older Gyromite cart, (the one that came with R.O.B, with the sleepwalking professor), if you crack it open you will see aFamicon EEPROM attached to an adapter leading out to the NES cart pins. You can yank that adapter out and use it for any Famicon game.
Not all Gyromite carts have the adapter, but if you pick up two carts it will seem slightly heavier if it's got the adapter.
If I'm not wrong this is just a DS case for the old Famicom adapter for the GBA SP. Anyway a great way to play Famicom/Nes on the go!
Its pretty cool for those that keep their cartridges for nostalgia's sake, but there are more efficient solutions (although illegal) to the problem that already exist. Emulator GBA/DS cartridges.
Nintendo may find it a good idea to develop a DS game cartridge which may act as an emulator and storage for legally downloaded classic games off of their server. The DS already has wifi connection and Nintendo already has a game database developed for the Wii.
They have the games and the venue for distribution. The only major cost would be the packaging/shipping.
The chip for the Famicom and the SNES is the same, just with a different case. So you probably could play all of your SNES games too, unless I am missing something.
The NES was the US version of the Japanese famicom. The game cartridges used the same ROMs and other chips, but US games had a DRM of sorts. There was a custom chip that unlocked a matching chip in the console. This was the main reason for the different cartridge connector. The ROM itself was unchanged and unprotected.
I wonder why anyone would bother with that kind of crazy hardware. Just about every vintage console game has been ROM dumped. The homebrew scene for the Nintendo DS is great. There are at least half a dozen cheap microSD adapters that will let you run all kinds of emulators, copy all your DS games to a flash card, play media, etc..
As already suggested, if Nintendo was smart, they'd release their own flash card to let you take your Wii's virtual console games with you on the DS.
cayton> Famicom = NES
Super Famicom = SNES
the company that is importing this gadget in Japan stared as a distribution company of American Porno videos in Akihabara but they gave up after realizing that US porno censored with mosaic doesn't make much sense...