I thought I'd post this as the C64 was one of the most popular 8 bits of all time. No doubt many HN'ers are familiar with it, perhaps a few aren't. The site linked is fairlight, an awesome old school demo group from back in the c64's (and Amiga's) heyday. The documents on the site are pretty much everything you need to get started, and the examples (last link at the bottom) are great at getting you up to speed on some common effects.

The best thing about this is that in learning how to code on the 64 you'll learn MOS 6502 assembly, which also enables you to get a head start on programming the Atari 8-bit computers and the consoles (2600 etc.) and the Apple I & II.

If you're looking for a weekend (or two) project, then you could do a lot worse than this.

So HN, what can you do with 64k of RAM and 1 Mhz CPU?