Wine is an implementation of the Windows API on top of X and Unix. It does not require Microsoft Windows, but can use native Windows DLLs if they are available. It provides both a development toolkit for porting Windows source code to Unix as well as a program loader, allowing many unmodified Windows programs to run on x86-based Unixes.
The Intel Software Development Emulator is a functional emulator for new and upcoming instruction set extensions. The emulator is based on the Pin dynamic binary instrumentation system (and XED). It emulates the new instructions in the SSE4, AES, PCLMULQDQ, and RTM, BMI1, and BMI2 Intel AVX, AVX2, and AVX512 instruction set extensions. This allows developers to gain familiarity with Intel's upcoming instruction set extensions.
XRoar is a cross-platform emulator for the Dragon 32, Dragon 64, and Tandy CoCo computers, all originally released in the early '80s. The emulator runs under Unix-like operating systems (including Mac OS X) and Windows, with older versions available for handhelds like the Nintendo DS and GP32.
Mini vMac emulates a Macintosh Plus, one of the earliest of the Macintosh computers. It can run old Macintosh software that otherwise couldn't be used on recent machines. Mini vMac requires a ROM image file to run, and so can be legally used only by those who own a Macintosh Plus.
uBee512 emulates all of the Microbee Z80 series of microcomputers, including ROM, Floppy and Hard disk-based models. Up to 2MB of extended memory is supported. The optional on board sn76489 sound IC is also emulated. The display may use SDL or OpenGL video rendering. Z80 PIO emulation includes tape, speaker, RTC, serial to PC RS232, and mouse peripherals. Parallel port peripherals include BeeThoven (AY-3-8910), BeeTalker (SP0256-AL2), Compumuse (SN76489), DAC, printer, and joystick. Many disk image types and floppy disks are supported. A joystick may be optionally mapped to keys. A large number of options are available as well as a built in OSD console.
ADTPro transfers disks to and from Apple II and Apple /// computers and the modern world using any of these communications methods: serial/USB, UDP via the Uthernet or LANceGS Ethernet cards, or audio via the Apple's cassette ports. ADTPro has comprehensive bootstrapping support for otherwise diskless Apple IIs. The home page includes extensive tutorials for getting started.