I have the Gecko and it can be used for just a couple of things.=20
Homebrew Games for Gamecube can be run from it using SDLoad in =
combination with an Action Replay and a crazy long code. I've done this. =
Animal Crossing 2? for the Japanese market offered the ability to =
take screen shots and save them directly to the SD card so they could be =
viewed and shared through your computer. I have not done this.=20
My understanding of why standard game saves don't work is SD cards =
and the gamecube memory card while electrically are very similar they =
use a different "Command Set" for reading and writing to their memory. =
At a really basic level (abstraction leaks) it's like IDE and SCSI both =
are harddrives that read and write data but they are not interchangable =
because their command set is different (and their wiring, I know).
Some homebrew games can read and write on SD cards because they are =
using their own programming calls to access the memory cards.