ScummVM is a program which allows you to run certain classic graphical point-and-click adventure games, provided you already have their data files. The clever part about this: ScummVM just replaces the executables shipped with the game, allowing you to play them on systems for which they were never designed!
ScummVM lets you run these adventures: Adventure Soft's Simon the Sorcerer 1 and 2; Revolution's Beneath A Steel Sky, Broken Sword 1 and Broken Sword 2; Flight of the Amazon Queen; Wyrmkeep's Inherit the Earth; Coktel Vision's Gobliiins and games based on LucasArts' SCUMM (Script Creation Utility for Maniac Mansion) system. SCUMM is used for many games, including Monkey Island, Day of the Tentacle, Sam and Max and more. Compatibility with supported games is continually improving, so check back often.
Among the systems on which you can play those games are Windows, Linux, Mac OS X, Dreamcast, PocketPC, PalmOS, AmigaOS, BeOS, OS/2, PSP, PS2, SymbianOS/EPOC and many more...