http://www.hidden-palace.org/

Remember when I said I would never beat a certain release? Well I was
wrong. Behold, over 1000 prototypes for various Sega consoles.

Quick numbers: 155 Sega 32x prototypes, 300 Game Gear prototypes, 464
Mega Drive prototypes, 94 Pico prototypes, 6 Gamecube prototypes --
1024 prototype overall (what a nice round number!), making this the
biggest prototype release in history (and probably ever to come). Just
multiply this by $100 (which is the average price of these things, and
many of them are MUCH more valuable) and you'll see how lucky you are
to get them free of charge.

There is lots of stuff here -- Sonic, Ristar, Tempo, and many other
high-profile, hard-to-find game prototypes which many of us played
years back and miss. Many with different features, levels, hidden
data.