ZXDS is an upcoming emulator of Sinclair ZX Spectrum for Nintendo DS, written by Patrik Rak. It is still in an early stage of development, but it already has some noteworthy features, like accurate emulation of Spectrum 128k (including sound) or TAP/TZX/PZX support.

Thanks to http://www.dcemu.co.uk for the news.

http://zxds.raxoft.cz/