StonX is an Atari ST emulator for X. It support many Atari apps, and runs very fast even on low-end machines (sub P75). It currently runs the standard Atari screen modes as well as expanded full screen. It is very portable and has successfully been used on Alpha workstations, Silicon Graphics workstations, HP PA-RISC systems, RS/6000 with AIX, proprietary systems by Siemens, PCs with FreeBSD, Suns with Solaris and SunOS, and others.
Xmame is the X11/Unix port of MAME. MAME is the Multiple Arcade Machine Emulator, an arcade (coin-op) video game emulator.