Before releasing an AGP installment, I scour the internet for any evidence of a commercially available release of the recordings or compositions.
Through these efforts, I have come across a number of sites offering avant garde music that is not distributed through the major outlets.
My first stop is typically Amazon.com. Their advanced search page enables one to search specifically by composer, composition, etc. The German, French, and UK Amazon sites often list recordings by composers from those countries that are not available at Amazon.com. CD Universe and JPC are other good places to check for commercially available CDs, some of which are not available through Amazon.
In addition, votaries of the avant garde with a little extra money in their pocket will find much of interest at the following sites:
Electrocd in Montreal carries a wide range of electroacoustic works, including the indispensible INA-GRM catalog.
Mimaroglu Music Sales is a one-man shop in Massachusetts, stocking many works that would otherwise be available to North Americans only from European outlets with correspondingly high shipping costs. Their catalog also includes the Creel Pone series of unofficial CD-R releases of out-of-print recordings.
Forced Exposure is another North American distributor for a wide range of avant-garde music.
CDeMUSIC is a music distributor operated by the Electronic Music Foundation in New York City. Their web site offers a wide variety of electroacoustic and avant garde music.
The Schott Music Shop has a large catalog of excellent avant garde music CDs, including many recordings from the Wergo catalog.
New World Records has published many recordings of avant-garde music. They are also now distributing the entire CD catalog of CRI records.
Unfortunately, many CRI recordings that originally appeared on LP are still out of print.
BVHAAST is a dutch label that carries a number of avant-garde CDs. Particularly interesting is the Acousmatrix series of electroacoustic works. Check out the 2CD collection of works by Gottfried Michael Koenig (Forced Exposure has this, if you are in North America).
Phono Suecia has an online shop that includes recordings of avant-garde works by Swedish composers.
Innova Recordings is the house label of the American Composers Forum. Among the many works they distribute is the Enclosures series of works by Harry Partch.
The London Sinfonietta markets recordings through its web site, including many recordings of modern music. The Ensemble Intercontemporain does not market its own recordings, but its site hosts a discography with links to amazon.fr.
Karlheinz Stockhausen makes his complete catalog available through his own web page. Other composers' pages I have come across include Francois Bayle's and Jean-Claude Eloy's. The latter has links to other Eloy-related sites. And The Living Composers Project is rich resource for information on, well, living composers.
The Man Who Planted Trees, by Jean Giono, is the official parable of the Avant Garde Project.
For a complete waste of time, be sure to visit hapaxlegomenon.
If you know of any resources I have missed, please let me know so I can include them on this page.