Z26 - Z26 is one of the best emulators for the Atari 2600.
MilkyTracker - MilkyTracker is an open source, multi-platform music application for creating .MOD and .
Steem Engine - Steem is an open source Atari STE emulator for Windows and Linux.
OpenMPT - OpenMPT is a popular tracker software for Windows.
Hataroid - Atari ST emulator for Android based on Hatari.
FamiStudio - FamiStudio is very simple music editor for the Nintendo Entertainment System or Famicom. It is designed to be easier to use than FamiTracker, but its feature set is also much more limited.