I thought I'd make a list of really cheap DS games like I did for PSP. These are all shipped/Sold by Amazon, so you can get free shipping. Maybe there's some DS fans still here to take advantage of them:
Animates: http://www.amazon.com/Animates-Nint...?s=videogames&ie=UTF8&qid=1354850201&sr=1-251
Band Hero NDS Bundle: http://www.amazon.com/Band-Hero-NDS...?s=videogames&ie=UTF8&qid=1354850067&sr=1-134
Beastly Frantic Foto: http://www.amazon.com/Beastly-Frant...?s=videogames&ie=UTF8&qid=1354850507&sr=1-543
Boogie: http://www.amazon.com/Boogie-Ninten...1?s=videogames&ie=UTF8&qid=1354849994&sr=1-81
Chaotic NDS with Trading Card: http://www.amazon.com/Chaotic-NDS-T...?s=videogames&ie=UTF8&qid=1354850441&sr=1-472
Don King Boxing: http://www.amazon.com/Don-King-Boxi...?s=videogames&ie=UTF8&qid=1354850602&sr=1-655
Guitar Hero on Tour Decades Bundle: http://www.amazon.com/Guitar-Hero-D...?s=videogames&ie=UTF8&qid=1354850329&sr=1-366
Guitar Rock Tour: http://www.amazon.com/Guitar-Rock-T...?s=videogames&ie=UTF8&qid=1354850037&sr=1-111
Ink Heart: http://www.amazon.com/Inkheart-Nint...?s=videogames&ie=UTF8&qid=1354850285&sr=1-319
Jam Sessions 2: http://www.amazon.com/Jam-Sessions-...?s=videogames&ie=UTF8&qid=1354850212&sr=1-263
Our House: http://www.amazon.com/Our-House-Nin...4?s=videogames&ie=UTF8&qid=1354849994&sr=1-84
Puchi Puchi Virus: http://www.amazon.com/Puchi-Virus-N...?s=videogames&ie=UTF8&qid=1354850105&sr=1-176
Puzzle Quest Galactrix: http://www.amazon.com/Puzzle-Quest-...9?s=videogames&ie=UTF8&qid=1354849958&sr=1-59
Rock Revolution: http://www.amazon.com/Rock-Revoluti...?s=videogames&ie=UTF8&qid=1354850067&sr=1-138
Shorts: http://www.amazon.com/Shorts-Ninten...?s=videogames&ie=UTF8&qid=1354850345&sr=1-378
Squishy Tank: http://www.amazon.com/Squishy-Tank-...?s=videogames&ie=UTF8&qid=1354850268&sr=1-303
The Chase: Felix Meets Felicity: http://www.amazon.com/Chase-Felix-M...?s=videogames&ie=UTF8&qid=1354850164&sr=1-216
The Golden Compass: http://www.amazon.com/Golden-Compas...3?s=videogames&ie=UTF8&qid=1354849994&sr=1-83
Animates: http://www.amazon.com/Animates-Nint...?s=videogames&ie=UTF8&qid=1354850201&sr=1-251
Band Hero NDS Bundle: http://www.amazon.com/Band-Hero-NDS...?s=videogames&ie=UTF8&qid=1354850067&sr=1-134
Beastly Frantic Foto: http://www.amazon.com/Beastly-Frant...?s=videogames&ie=UTF8&qid=1354850507&sr=1-543
Boogie: http://www.amazon.com/Boogie-Ninten...1?s=videogames&ie=UTF8&qid=1354849994&sr=1-81
Chaotic NDS with Trading Card: http://www.amazon.com/Chaotic-NDS-T...?s=videogames&ie=UTF8&qid=1354850441&sr=1-472
Don King Boxing: http://www.amazon.com/Don-King-Boxi...?s=videogames&ie=UTF8&qid=1354850602&sr=1-655
Guitar Hero on Tour Decades Bundle: http://www.amazon.com/Guitar-Hero-D...?s=videogames&ie=UTF8&qid=1354850329&sr=1-366
Guitar Rock Tour: http://www.amazon.com/Guitar-Rock-T...?s=videogames&ie=UTF8&qid=1354850037&sr=1-111
Ink Heart: http://www.amazon.com/Inkheart-Nint...?s=videogames&ie=UTF8&qid=1354850285&sr=1-319
Jam Sessions 2: http://www.amazon.com/Jam-Sessions-...?s=videogames&ie=UTF8&qid=1354850212&sr=1-263
Our House: http://www.amazon.com/Our-House-Nin...4?s=videogames&ie=UTF8&qid=1354849994&sr=1-84
Puchi Puchi Virus: http://www.amazon.com/Puchi-Virus-N...?s=videogames&ie=UTF8&qid=1354850105&sr=1-176
Puzzle Quest Galactrix: http://www.amazon.com/Puzzle-Quest-...9?s=videogames&ie=UTF8&qid=1354849958&sr=1-59
Rock Revolution: http://www.amazon.com/Rock-Revoluti...?s=videogames&ie=UTF8&qid=1354850067&sr=1-138
Shorts: http://www.amazon.com/Shorts-Ninten...?s=videogames&ie=UTF8&qid=1354850345&sr=1-378
Squishy Tank: http://www.amazon.com/Squishy-Tank-...?s=videogames&ie=UTF8&qid=1354850268&sr=1-303
The Chase: Felix Meets Felicity: http://www.amazon.com/Chase-Felix-M...?s=videogames&ie=UTF8&qid=1354850164&sr=1-216
The Golden Compass: http://www.amazon.com/Golden-Compas...3?s=videogames&ie=UTF8&qid=1354849994&sr=1-83