It may not have a fancy-looking site, but the International Arcade Museum is an amazing place on the internet.
They have a growing database of arcade games, pinball machines, slots, music machines, vending machines and more. Gimmick machines and novelty devices from the past galore, most pages with photos.
IAM also offers auction listings for people to exchange their rarities.
You gotta check this out, I could spend hours on this site reminiscing about the past.