Some that might interest folks here:

• Real Player - The inventors of streaming & the poster child for enshittification
• iRiver - perhaps the first major MP3 (and OGG!) player. DRM & iTunes not required.
• Napster - P2P for the early adopters
• KaZaA, Limewire & Bearshare - P2P for the masses. (And BTW the source of my user name: klu9 = KaZaA Lite User 9)
• MP3.com - At first indie artists uploading their own materials, then users uploading their own CDs
• Radio.Blog.Club - Embed an MP3 in your blog
• Grooveshark - Streaming all music
• Usenet - A shadow of its former self but still a bastion of binaries

Personally, got started with Audiogalaxy, went all in with Morpheus & KaZaA Lite. Loved Grooveshark, discovered so much there. Still have a few RMVB (Real Media Variable Bitrate) videos burned on DVD-Rs somewhere.