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.
MBCD (MultiBootCD) is a shell script to make a customized CD-ROM that can boot any kind and any number of image files. Currently, 4 types of images are supported: floppy images (1.2M, 1.44M, or 2.88M), Knoppix-like images, kernel-binary images (e.g. memtest86), and the Windows XP Recovery Console.
Nonpareil is a microcode-level simulator for HP calculators introduced between 1972 and 1982, including the HP-35, HP-45, HP-55, HP-25, HP-34C, HP-38C, HP-41CV, HP-11C, HP-12C, HP-15C, HP-16C, and other models. The necessary microcode is included, as is a microcode assembler. The GTK+ toolkit is used for the user interface.
Aliados is a CP/M 80 emulator. Instead of emulating a machine and running some variant of CP/M on it, it emulates only the microprocessor and captures all CP/M system calls to execute natively. It does not need to create disk images, but reads and writes on the native filesystem all files that match the CP/M naming conventions.