If you have DOS games and a Macintosh but not a windows PC, you can play them! No expensive software needed. I have not tested this out on any Mac OS lower than 10.4. I am sure it will work on OS 10.4 and above.
This instructable only details software games. If you have something on a floppy disk then you'll need hardware to put it on.
There are several games floating around on the net. I decided to use freedoom to play. Freedoom is a .wad file, so you need another program to run it. I used Boom 2.02 becaue it works in DOS. I've not tested it on windows, but I'm sure it'd run fine in either DOSBox on Windows or in Command Prompt.