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Recently the Mini vMac for Android was released. It emulates the hardware for a Mac Plus computer. You got to supply the ROM image on a disk file. You also need to supply the actual Mac OS. This program is distributed for free under the GNU GPL. Upgrade to the Mini vMac II for $2. This upgrade emulates a Mac II. You can run 68k Mac apps on this paid version.
If you want to really go large, I hear the Basilish II is a more powerful Mac emulator. It emulates the 68040 Mac. This program can run up to the Mac OS 8.1. The Mac vMini only supports System 7. Then again the Mac vMini can be fun. There was plenty of shareware and freeware from the old days such as Core War, HyperCard, and Risk.