I've been cleaning up a sprite exporting tool I wrote a few of years back when I did a bit of gba coding, it's what I've been using for my rts. It's somewhat user friendly at the moment, so I figured I'd release it publically.
I've never tried other people's exporters, so I have no clue how it compares, or if it does anything differently.
Also included is some sample art to test it, and some exported files that it generated, so there's no need to download it to see what it will do, just grab the sample pack.
I'll put up some nds code to load and display an exported anim soon.