The 'Other' Cartridge Hacker
While DarkFader is the first to interface with and dump a DS cart, there is another hardware hacker on the dslinux.org boards, who is building his own custom DS interface.
Natrium42 has built a cart interface that can connect to a computer with either a parallel or serial interface. Using DarkFader's code he has managed to dump the first 90 characters or so of the header, but has not yet managed a complete dump. His interface unlike DarkFader's is made from a few relatively cheap components so it might be more promising to those of you who don't want to shell out for an FPGA board.