The port of Stella (atari 2600 emulator) to the Nintendo DS is well under way. Here is how the project is coming so far:

TheChuckster:
I am working on a port of the Atari 2600 emulator Stella. So far almost the entire code base has been ported. Download a ROM and put it in the data directory. Name it "pacman.bin" and recompile. The emulator will load, MD5 sum, and execute it... It won't work in [any DS] emulators... [It] has been quite optimized and plays at a smooth playable speed now thanks to a faster framebuffer drawing routine. I will continue to work on it though and add sound.

You can get the source in our NDS Download section [here]