I just bought a Nintendo DS and a SuperCard for homebrew..
And once installing the devkitARM, ndslib, gbalib and the you will ralize that you need ndstool for linux... I haven't find it anywhere but in the cvs source forge repository, so I installed cvs, got the source and here is the binary: ndstool
If you want to compile it yourself these are the magic words you need to type:
cvs -d:pserver:anonymous@devkitpro.cvs.sourceforge.net:/cvsroot/devkitpro login
cvs -z3 -d:pserver:anonymous@devkitpro.cvs.sourceforge.net:/cvsroot/devkitpro co -P tools/nds/ndstool
enjoy!