get sdload and burn it as a gc disc.
or.... its on the wiikey setup disc, you can use it from there even tho you have a cyclowiz, doesnt matter as the wiikey setup disc loads in any modded wii/cube.
just pick sdload from the wiikey disc menu, dont worry about not having a wiikey, i use it in my cube as well as my wii
you can load emulators from your sd card, get the .dol files for them from
http://gcemu.dcemu.co.uk/.
its a good homebrew site, has also gc homebrew, like cubedoom. doom works straight from the sd card with sd load as well as the other homebrew games.
just remember all gamecube applications you put on the sd card (emu's, homebrew games etc) must be in .dol format.
ps. using it as a memory card is kinda craptacular, it works with jap animal crossing.. and urm... urm.. think thats about it. there may be 1 or 2 more games it works with.