Porting Kit - Install Windows Games in Mac OS X natively and easily and for free with Wineskin technology
Vineyard - Windows programs on Linux, easily
CodeWeavers CrossOver - Don't buy a Windows license, don't reboot and don't use a Virtual Machine. Try a free trial of CrossOver to run your Windows software on Mac, Linux and Chrome OS.
Lutris - Lutris is an open source gaming platform for GNU/Linux.
PlayOnLinux - PlayOnLinux will allow you to play your favorite games on Linux easily
RetroArch - RetroArch is a frontend for emulators, game engines and media players.