Free NDS  Roms can be found at this great site. New NDS Rom titles added daily. I’ve listed a few of there most recent NDS Roms.

Genio de las Palabras (S)(iND)
Cnae Aprende con Nosotros (S)(iND)
Spore Hero Arena (E)(Xenophobia)
Cate West The Vanishing Files (E)(Xenophobia)
HMH Vokabeltrainer Spanisch (G)(BAHAMUT)
Mario And Sonic At The Olympic Winter Games (U)(Xenophobia)
Pokemon Mystery Dungeon Explorers of Sky (U)(Xenophobia)
Iron Master (J)(2CH)
Tago Akira no Atama no Taisou Dai 4 Shuu Time Machine no Nazotoki Daibouken (J)(BAHAMUT)
Tago Akira no Atama no Taisou Dai 3 Shuu Fushigi no Kuni no Nazotoki Otogibanashi (J)(BAHAMUT)
Knigge Spielend zum guten Benehmen (G)(BAHAMUT)
Mario and Luigi Bowsers Inside Story (E)(Xenophobia)
Intelligenztrainer fuer Kids (G)(iND)
Gripskids Sachkunde (G)(iND)
Baby Wildkatzen (G)(iND)
Shin Megami Tensei Strange Journey (J)(2CH)
Los Lunnis (S)(iND)