They're for the nintendo gameboy advance e-reader. It used very condensed dot codes on the sides of cards to store small amounts of archived data, with most of the graphics and sounds already stored onto the e-Reader itself.
Since the dots are so tiny, they can't simply be scanned or copied. So these dumps are basically the dots in data form. If you have a printer that can print in 600dpi or higher, you can grab these files and a special printer application that reads them, and print out some cards that can be read by the e-Reader.
If you don't have an e-Reader or fancy printer, no$gba has a method of loading cards via the data dump. I did it once but don't remember exactly. I think something pop's up when you're in scan mode for the e-Reader, and then you select the card. That or it's just in one of the options somewhere.
It's pretty neat actually, and useful if you want to get certain things in games like Animal Crossing for the gamecube.
I don't see how this is really news though, since this is an ongoing effort on behalf of No-Intro, but eh.