little info to the expo on wtf this stuff is?
god didnt anyone read zzk's post.
anyway...
http://www.linker4u.com/pp/success.asp - a device that goes into the gba slot. you put a sd car into it and the ds will pull the info from the sd card. so you can play DS roms, gba roms, NES roms, snes roms, etc. also it can play movies listen to music and view text files. plus you can use hombrew ds equipment.
http://www.mrmodchips.co.uk/catalog/product_info.php?ref=20&products_id=396&affiliate_banner_id=1 passme 3 - the device that lets the ds read ds data from the sd card in the gba slot.
http://www.flash-memory-store.com/qmemory-sd-150x-4gb.html sd card of choice - 4gb sd card.