Yesterday, there were reports that none of the flashcarts for the DSi works on the Nintendo 3DS. Today, one flashcart is to be confirmed working and it's the R4!
As most of you know today was the 3DS preview event in New York. Due to some problems on my part I wasn't allowed in so I don't have any direct info for you. But I do have the next best thing, a 3DS round up from around the interwebs.