XRoar is a Dragon and Tandy CoCo emulator for Linux, Unix, Mac OS X, GP32, Nintendo DS and Windows32.

Features:

Emulates Dragon 32, Dragon 64, Tano Dragon, Tandy CoCo 1/2.
Emulates DragonDOS, Delta and RSDOS disk systems.
Raw and translated keyboard modes.
Reads and writes virtual cassettes (“.cas” files).
Reads audio files as cassette input.
Reads and writes DMK format virtual floppy diskettes.
Reads (and supports in-memory writing of) JVC and VDK format virtual floppy diskettes.
Custom snapshot format; no “.pak” support yet.

Changes:

More accurate single-bit sound (fixes issues with the game “Demon Attack”). Configurable because it also introduces the real-hardware artifact of buzzing/clicking in some games.
Supports changing the SAM RAM organisation.
NDS: Much improved video, sound and user-interface.
GP32: Chatboard support working again.

http://www.6809.org.uk/dragon/xroar.shtml