www.noisemusic.org is one of the best places for top-notch
Drum & Bass,
Trip Hop,
Breakbeat,
Electronic and
Experimental music. Starting out in 1995, the site has consistently brought out music of great quality, all from 100% never-heard-of musicians.
Up until around 1998, tracks were brought out in a variety of module formats, such as IT, XM and even Buzz. MP3 has since replaced these formats, since using lots of high quality samples can drive up the module size quite a bit. MP3 also allowed musicians to process the track sound after completion.
Noise has a slew of capable musicians, such as st0te, shawnm, Elysis, Astradyne and pinku vääty to name a few.
Me personally, I eventually took advantage of a friends DSL connection to d/l the whole archive (some 700MB).