FirebrandX's NES Composite Palette Project documents years of work trying to reproduce the colors of original Nintendo hardware across CRTs, emulators, RGB mods, and modern displays. The problem is much messier than picking 64 nice colors.
The Gryphel Project's Mini vMac preserves the software environment of early 680x0 Macintosh computers, combining a tiny emulator with documentation, build tools, disk images, and legally redistributable classic Mac software.
Stephen Tjasink and Paul Rahme's Bubble Bobble Info Pages preserve cheats, item behavior, hidden messages, version differences, level data, and ROM-derived technical details from Taito's 1986 arcade game.