VirtualBox is a powerful open-source full virtualization software that allows a user to run one or more “guest” operating systems simultaneously inside “virtual machines” on a single physical “host” machine. It supports a wide variety of host platforms (Linux, Windows, macOS, Solaris, etc.) and guest OSes, enabling, for example, running Linux on a Windows PC, running Windows Server on a Linux host, or even legacy OSes in a controlled environment.
VICE is an emulator collection which emulates the C64, the C64-DTV, the C128, the VIC20, practically all PET models, the PLUS4 and the CBM-II (aka C610). It runs on Unix, MS-DOS, Win32, OS/2, Acorn RISC OS, BeOS, QNX 6.x, Amiga, GP2X or Mac OS X machines.
KEGS is a portable Apple //gs emulator for Linux, OS/2, HP-UX, and Solaris. It is very accurate and quick, running at an emulated 10MHz on 200MHz machines.
This version of KEGS is using SDL (Simple Directmedia Layer) for more portability.
PHPterm is a terminal/shell emulator for PHP which let's you execute shell commands just like in a shell, but all within your browser window over the HTTP protocol.
It aims to provide the look and feel of konsole, the KDE terminal.