The Nintendo DS has had a very talented homebrew scene right from the very start thanks to the popularity of DS Flash carts such as the R4. This page will list just a few of the amazing homebrew apps developed by the scene.
If you are interested in browsing a full list of all DS homebrew developed then you should visit the GameBrew wiki page for this: List of DS homebrew applications - GameBrew - a wiki dedicated to Video Game Homebrew.
Steve Chapman from Panocamera.com has built a very impressive homebrew application and hardware interface to connect his DSLR camera to his Nintendo DS 1.
The story goes that he grew tired of lugging around his heavy cumbersome energy-hungry laptop when using his DSLR camera and wanted to find a lighter solution 2.
It uses the Gameboy Advance cartridge slot to connect to the camera so has presumably created his own circuit board to convert the two data interfaces.
He has even managed to add voice recognition support to take a photo when he says a word, saving hundreds of dollars on buying a retail solution for the task 2.
The Moonshell multimedia player allows you to play Movies right from your DS! This was pretty huge in 2007 when having a portable way to watch videos was much less common 2.
￼ DSTwitter was a very simple twitter client for the Nintendo DS, it worked very well to read and even reply to tweets. Unfortunately as it only ever has support for basic Twitter authentication and no OAuth support, it no longer works as twitter removed basic auth in 2009 3.
Still Alive DS is a nice puzzle platformer that borrows concepts from Portal.
LoneWolfDS is a very unique homebrew game in that it takes one of the physical adventure gamebooks written by Joe Denver and converts it into an interactive story with RPG like elements 4.
The DS has fairly limited hardware so full speed emulation of SNES and Mega Drive games are pushing the machine to its very limits. However there are a few excellent emulations for the DS, especially for more limited systems such as the original Gameboy/GBC and the Sega Master System.
You can view a full list of emulations available for DS over on GameBrew: List of DS homebrew emulators - GameBrew - a wiki dedicated to Video Game Homebrew.
The Nintendo DS Wifi Connection or WFC was a way to play Nintendo DS games online, however Nintendo shut down their servers in 2014.
Thankfully some smart developers have spent their time creating an open source replacement for the game servers, managing to bring back most of the functionality including leaderboards and matchmaking [^].