Modchips

There are many NDS modchips (also known pass passme or flash cards). You can click on them to buy from Amazon.

THE M3 DS Simply

My favorite is the M3 DS Simply (Used to be known as the R4). I like it because its cheap and very easy to use. It comes with a slot for a micro SD card. You can get it with a 1Gb Micro SD Card or with a 2Gb Micro SD CardThe only problem with the M3 DS Simply is that it can’t run Gameboy Advanced games. For that you need a slot 2 device.

R4 DS Revolution for DSR4 DS Revolution for DS

I am pretty sure this is the same hardware as the M3 above, but prices maybe be slightly different.There is also a version that comes with 1GB MicroSD Memory Card + Free Games All in all a very good card, but the same as the M3 Simply really. Given the choice I would go for the M3 simply over this as its newer.

Supercard Lite SuperCard Lite

The SuperCard Lite has half a gigabyte onboard memory and a mini sd card slot. It plugs into the GBA slot so it can run GBA games as well as DS and homebrew games and applications.