Jeff Atwood (coincidentally the cocaine-dusted, AK-toting godfather of our comment system) writes at length about the absolutely fabulous things that the tiny, supremely adaptable Raspberry Pi computers have done for the emulation scene. His posting doubles as a useful how-to for those unfamiliar with the drill.
1. The ascendance of Raspberry Pi has single-handedly revolutionized the emulation scene. 2. Chinese all-in-one JAMMA cards are available everywhere for about $90. 3. Cheap, quality arcade size IPS LCDs of 18-23".
This is most definitely the funnest and cheapest way to get into arcade emulation when you want to step beyond apps. If you're not into messing around with linux and configuration files and whatnot, an Intel Compute Stick (which comes with Windows) is a more expensive but easier path than a Pi. But you'll still have to deal with the hardware. Read the rest
Sprybug at the Atari Age forums published an Atari 2600 version of Super Mario Bros. with 16 levels, world bosses, pipes and even flagpoles.
The collision detection with the playfield blocks isn't 100% perfect, but it's close. Still something I have to work on if I have the cycle time to. So, have fun, and yes I included music and sound effects.