The Internet Archive is an online library of digital cotent. In their Audio section, they have a directory of netlabels. The link above leads to the netlabel list with descriptions; for the home page of the section, go to http://www.archive.org/details/netlabels. The Internet Archive also hosts music for individuals, but the quality of the musicians varies.
Phlow's Netlabel Catalogue
They have 112 different categories that netlabels are orginized by for the genres of music they host. Many of these netlabels are also listed at the Internet Archive, but there are several still that are unique to Phlow (especially the newer ones). They also have netaudio charts and streaming music of netaudio.
From the Internet Archive: "The 8bitpeoples first came together in 1999 as a collective of artists sharing a common love for classic videogames and an approach to music which reflected this obsession. Our primary interests were to provide quality music for free and most importantly to have fun. In the years since, we have grown in rank and expanded our goals."
From the Internet Archive: "Camomille is a free netlabel project to provide high quality music in .mp3 format to the idm, ambient, blip-hop, glitch, drill&bass, new age, noisescape, experimental, electronica listeners."
From the Internet Archive: "Kahvi is a net.label dedicated to releasing freely distributable music in .OGG format - we specialize in the more ambient and chilled out (relaxing) genre, though we come up with a few surprises along the way. All the tracks are created by unsigned artists usually composing on their home studios. Some even went on to being signed by major labels and are now touring the world circuit, performing live and promoting their music. What our visitors have said about us: 'Beautiful site, love the music, and the great artists!' 'When I spend 100 hours of tedium exploring the Internet, there is only 10 seconds of pleasant surprises which give me what i'm looking for, and Kahvi is one of them... thanks!'"