[Updated: Thanks to Mike for pointing out I originally got my links mixed up for this entry. Below is proper text for the original link, and a new link for what I originally intended to post.]
Project 64 collects and transcribes old manuals and documentation for Commodore computers, including the C64, C128, the Amiga, and assorted software.
Power64 is a Commodore 64 emulator for Mac OS X. Shareware, demo limited to 10 minutes, but a definitive emulation for OS X. Good sound emulation, a nice disk drive management interface, and an adjustable anti-aliased display.
Project64 is actually a collection of documentation. Perhaps you had another emulator in mind?