melonDS v0.4 is released. melonDS is an open source Nintendo DS(NDS) emulator. melonDS is part of a second wave of DS emulators. There are a few other emulator projects that are part of it, which you might have already heard of. Either way, check them out!

melonDS Features:
* almost-complete 2D graphics
* 3D graphics (software renderer) with texturing, alphablending, lighting
* input: keyboard and joystick, touchscreen
* backup memory
* booting from the BIOS
* resizable video output window, preserving aspect ratio of individual screens

melonDS Changelog:
• implement access modes for certain IO registers that were unhandled
• actually implement RCNT instead of hardcoding it
• wifi: emulation of multiplayer cmd/reply/ack transfers
• wifi: more accurate RFSTATUS/RFPINS
• wifi: some games can go into multiplayer now (Pictochat, NSMB, Pokémon known working)
• improved savemem detect heuristic
• implement firmware write, fix SPI bugs
• accurate emulation of 'main memory display FIFO'
• 2D: fix render/capture order
• 2D: implement mode6 large BG
• 2D: fix bitmap BG sizes
• 2D: fix rotscaled bitmap sprites
• 3D: fix missing term in MatrixTranslate
• 3D: fix toon highlight mode
• 3D: fix boxtest bug
• 3D: accurate viewport transform
• 3D: polygon Y-sorting
• 3D: more accurate interpolation, still not perfect
• 3D: more accurate Z and W transforms, fix some cases of Z-fighting
• 3D: separate polygonID attributes for opaque and translucent pixels
• 3D: start documenting and implementing depth test edge cases
• emulate delays for SPI transfers and div/sqrt
• misc bugfixes/additions as usual

How to use
melonDS requires BIOS/firmware dumps from a DS. You can dump them with the following dumper.
The files must be placed in the same directory as the melonDS executable, as follows:
* bios7.bin -- ARM7 BIOS, 16KB
* bios9.bin -- ARM9 BIOS, 4KB
* firmware.bin -- firmware, 256KB or 512KB

Note: the DS-mode firmware in the 3DS isn't bootable. It only contains the bare minimum required to run DS games. Be sure to enable direct game boot when using a firmware dump from a 3DS.

Settings
Emulation: settings related to emulation. For now it lets you enable direct game boot (directly runs the game instead of going through the firmware).
Input: allows you to configure keyboard and joystick input. You can change a mapping by clicking the corresponding entry, then pressing a keyboard key or joystick button. For now, joystick input uses the first joystick available if multiple joysticks are plugged.

Download: melonDS v0.4
Source:Here