ZXDS is an emulator of Sinclair ZX Spectrum for Nintendo DS, written by Patrik Rak. It is steadily reaching a mature stage of development, and it already has some noteworthy features, like accurate emulation of Spectrum 48k, 128k and Pentagon models (including sound), or support for TAP/TZX/PZX tape files, TRD/SCL disk files and RZX playback files. Read more about ZXDS v0.9.9 (Beta 2) (Spectrum emu for NDS)
Once in a while someone bothers to create a demo for the Vectrex and Where Have All The Pixels Gone? by cmucc is actually a quite good one! Vectrex forever! And guess... they even managed to add Nyancat ;) Read more about Where Have All The Pixels Gone? (Vectrex Demo)
XChat is an IRC chat program allowing you to join multiple IRC channels (chat rooms) at the same time, talk publicly, private one-on-one conversations etc. Even file transfers are possible. Read more about XChat v2.8.8.1 (Pandora Application Port)