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.
Atari800 is an Atari 8-bit computer (400, 800, and XL and XE series) and Atari 5200 game system emulator for DOS, Windows, Amiga, Atari ST, Mac, and Linux/UNIX. It includes support for Atari cartridge ROMs, popular Atari disk images files, running Atari binaries directly from the host system, and accessing the host filesystem from within the emulated Atari.
Frodo is a free, portable C64 emulator. It focuses on the exact reproduction of graphical effects possible on the C64, and comes in three "flavors" (Frodo, Frodo PC, and Frodo SC) with increasingly higher quality of emulation, but at the cost of higher processing power requirements. Frodo has been ported to a number of systems, including handheld computers. The Unix version can use either SDL, X11, or SVGAlib to display the graphics.
The Free Unix Spectrum Emulator (Fuse) is an emulator of the 1980s home computer and various clones. It emulates the Spectrum 16K, 48K, 128K, +2, +2A, +3, +3e, and SE, the Timex TC2048 and TC2068, the Pentagon, and the Scorpion. Almost all the common Spectrum emulator file formats are supported, including .rzx input recordings, .tzx tape images, and .szx and .z80 snapshots.