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.