There are a lot more than that one, too! QDQ is the original, but Quake done Quicker and the Rabbit Run are also required viewing. And then you move on to things like Super Metroid... It was this stuff that got me into the Speedruns (and TAS) scene. Your two main resources for this are:
for "tool-assisted" speedruns or time attacks, meaning using emulators and often doing truly insane frame-by-frame optimization and memory-state-manipulation.
One of my favourites; not technically a speed run, but a festival of glitches being used to corrupt memory in a very specific way, using only the regular gameboy inputs :)
http://speeddemosarchive.com/
for "real" speedruns (the rules are complicated, but often on original hardware, captured on video) and
http://tasvideos.org/
for "tool-assisted" speedruns or time attacks, meaning using emulators and often doing truly insane frame-by-frame optimization and memory-state-manipulation.