Nothing that is quick nor easy to set up. What exactly are you trying to do?
I want to write an application for the DS that is used in bridge clubs. During the game the players record the score on each hand. This would be written to some file, a text file I guess unless there's another format the DS likes, and either transferred continuously to the PC after each hand, or transferred after the game is over by selecting an option. Or they could be transferred to a single DS (if straight to PC wasn't possible), and the SD card in the flashcart could be put in the computer afterwards. (In a bridge game, multiple tables are in play so it would be super impractical to take the SD card out of every flashcart out of every DS to put in the computer, nobody would go for it)
There are already specialised machines that do this (called BridgeMates and BridgePads) but they are quite expensive and of course the features are static. I can think of lots of good features that would be possible on a DS. They also crash a lot (which really discturbs the game as you have to switch to paper scoring), not sure if I'd be able to improve on that but if I could that would be great of course.