Your 3DS cart games saves can be moved to your PC with this Japanese device from Cyber Gadget, called Cyber Save Bank. It's a USB device that lets you plop in your 3DS games to pull their save data as a file. I need this for my Shin Megami Tensei IV save, and one day I'll need it for my Pokemon stuff.
You can also reset the save data, which is kind of scary.
I wonder if this will handle DS carts as well.