Video Game Atlas

Via Joystiq, a very worthy site that's sure to stoke the fires of nostalgia. VGMaps.com is an altas for games old and new, with extremely impressive stitched together screenshot displays. Some of my personal favorites include Zebes, The Maniac Mansion, and the FFI Overworld.

Re:How did they generate them?

[snuf23]

The SID chip [kubarth.de] was a 3 voice electronic synthesizer. Emulators have never quite matched the sound, and you can even purchase a hardware PCI card (Hard SID) if you are so hardcore you need that you need the original sound. In fact, Denver band Mr. Pacman [gogomagazine.com] uses a Commodore 64 to get the true '80s sound they need.
There are SID emulators as well as SID collections such as The High Voltage SID Collection [c64.org].
Remixes of old video game music is also all over the web. Check out remix.kwed.org [kwed.org] for excellent remixes. The ones by Perhaps a Doobie and particularly amusing. Check out the Monty on the Run Hi-Score theme and the 1942 High-Score theme. Classic stuff.