Consider yourself lucky to be alive in a time when the Internet provides the means to satisfy your desires. MP3s lie thick and fast across the landscape of the Web. People post them on their home pages. Companies stockpile them on their sites. There are collections of unsigned bands, fan homages to individual low-profile acts, and hot singles for free download at big shopping sites.
Individuals post songs on newsgroups.
There are search engines solely for MP3 files, and there are the decentralized music libraries of Gnutella, Napster, and their evolving progeny, though legal challenges threaten these. Spend a little time browsing some of the larger MP3 sites or use search engines, and you'll come across songs and links aplenty. Downloading from the Internet depends primarily on connection speed. Broadband access allows for whip-fast downloads. You can make these directly from your CDs to a CD-R disc, mix and match music and MP3 files, or make a collection of your favorite playlists.