Naxos

On their website, Naxos calls itself, "The World's Leading Classical Music Label." In recent years, they certainly have been one of the most successful, offering good quality recordings at a fraction of the price you will find elsewhere. Their website, naxos.com, is also becoming the most important resource I know of for cheaply exploring the full classical music catalog. For $20 per year, you can gain access to their entire CD collection in streaming FM quality audio. That is over 5,000 CDs worth of music.