Since the beginning of times, every platform has had some titles that are sorta kinda games, but not quite. Call it edutainment, interactive toys or non-games, all those games were there, quietly selling and entertaining lots of people. With the DS wild success among people that usually wouldn't play games, the non-games got the push they needed to become relevant again, resulting in a plethora of non-traditional games. Some of them are quite good, and this section is for them.
America's Test Kitchen: Let's Get Cooking
A nifty cookbook with 300 recipes explained step by step. Don't worry if you are completely clueless in the kitchen, it has an explanation for almost anything (some explanations in video), a list of acceptable substitutes for many ingredients and you can make a list of the things you need to buy for a particular recipe. Each step is spoken aloud by your DS and the voice recognition is handy when you have your hands busy. One common problem is that the voice recognition can pick up ambient noises (like pans hitting each other) and sometimes interpret them as instructions, which can be annoying, but nothing gamebreaking.
Kanji Sonomama Rakubiki Jiten
Japanese to English Dictionary
A good and cheap Japanese to English dictionary. Obviously uses the stylus, but it has plenty of handy options mapped to buttons, so try everything.
Use this game to transform your DS into a guitar. A really small and rectangle-shaped guitar. Assign guitar chords to a D-pad direction and strum with the stylus on the touchscreen. It's fun to experiment with and allows you to save your performances. The sequel adds a Guitar Hero-esque mode where you strum specific chords along one of the songs available and allows you to strum individual strings in a chord but cuts the chords you can assign to the buttons from 16 to 8. Still enough for a lot of songs.
Minagara Oreru DS Origami
This is just like a cookbook, but the instructions are for folding paper to make origami instead. The instructions are given as animations, which are clear enough to follow, and since your hands are gonna be busy the voice control is extremely useful. In Japanese but completely usable even if you don't know the language (brotip: next = tsugi; previous = mae; once again = mo ichido).
My Japanese Coach
If you want to learn Japanese, this is a good place to start. Practice your writing on the touchscreen, use the mic to record your voice and compare it with the sample to practice your pronunciation. The pronunciation in the game is good, the lessons are bite-sized but plenty and most of the minigames to practice vocabulary are fun and useful (not every minigame, though, Spelltastic sucks). The best way to use this game imo is right before or along a proper Japanese course like Genki or Minna no Nihongo.
Actually pretty fucking good to learn kana, not to so much for the more advanced stuff.
Personal Trainer: Math
WOOHOO! A collection of MATH EXERCISES! Focuses on the four basic operations and its main attraction is a 10x10 blank grid that you have to fill with numbers. There's something strangely amusing about solving a bunch of simple arithmetic problems in a row that makes playing this game quite a relaxing experience. Unless you have a distinct allergy to numbers, this is definitely better than it sounds.
This is like MSPaint, but your tools simulate real pencils and real brushes, and has art lessons in case you want to learn a thing or two about painting. The DS game mixes both DSiWare titles Art Academy First and Second Semester's lessons, adding more reference photos and more frames for your work, but on the flipside you can't save to an SD cart as with the DSiWare ones. It's DSi enhanced, so you can use the camera if you have one.
Korg DS-10 Plus
The much improved sequel to Korg DS-10, Korg DS-10 Plus isn't a music game, it's a portable analog synthesizer, so it could be complicated to use unless you are familiar with that kind of thing or curious enough to try every knob and switch to see how this works (or read the manual). In any case, with two synth tracks, four drum tracks, tone tweaking, audio processing and multiplayer capabilities this software will turn your DS (and probably yourself) into a techno-pop machine. And if you are using a DSi, this app uses the extra power to double your tracks and your channels.
100 classic books (US) 100 classic book collection (UK)
Hold the DS sideways and flip pages with your fingers for some ebook reader goodness. Despite having only public domain works that you can get for free on the interwebs, this is definitely a game you should consider getting if you like reading. One of it's best features is that you can grade each book you finish in a series of aspects and upload those grades to the Nintendo Wifi Connection, so if you are not sure what to read next (or if you are simply curious about which book is collectively considered the most bizarre/funny/profound) you can consult with the Nintendo hivemind. Other nice features are background sounds (so you can pretend to be reading in a summer day/an airport/the beach), three bookmarks per book and a curious recommendation system (at least in the UK version).
ALSO I HOPE YOU ENJOY CHARLES DICKENS BECAUSE DAY-UM!