A bunch of (small) images, that work in the emulator.
- KolibriOS: http://kolibrios.org/en/download
- FreeDOS: http://www.freedos.org/
- FreeDos software: http://www.freedos.org/software/ and http://www.pouet.net/prodlist.php
- Linux: Self compiled Kernel and Busybox. A working image can also be found here: http://wiki.qemu.org/download/linux-0.2.img.bz2
- Windows 1.01: http://vetusware.com/ (can't remember exact link)
- Sol OS: http://www.oby.ro/os/