Very fond memories of using Audiogalaxy, and also soulseek.
Soulseek especially had a community where you found someone who was into the same kind of music as you (obscure breakcore! japanese garage punk!) and could browse their collections, and chat to them also! What a wonderful way to make music friends and get good recommendations.
https://nicotine-plus.org/ for the free software/UNIX people, by the way.
I don't use it anymore since getting into private trackers because the network (central server) is proprietary, the experience is much less polished than BT and I want to be sure of the release (LABEL/CATALOGNUMBER) I'm downloading.
Audiogalaxy was awesome. I loved how you could browse every file that had ever been online, rather than just what was online now, and queue them up for when they came online again. I’d just leave it running on our dial up connection when everyone went out of the house (no dedicated line so you’d clog up the phone, the good old days haha) and then come back to some exciting downloads I’d totally forgotten that I ever queued
On the more legal side of services was the original last.fm - as a pupil/student I spend days/hours discovering new music there. Not only due to automatic recommendations, but a lot of time by browsing other people's listening habits - just like browsing the music collection of someone else on soulseek.
Did I hear Soulseek? Look for slskd in github. I had a tear on my face when I could find people sharing japanese math rock :)
It's still there!
SSK is the best of anything mentioned here. You can find everything. Community is extremely big and it is there 25 years and will hopefully be another 25. The coverage level is so good that you can find any release in loseless format. There are folks having millions of audio files and 50TB of highly organized data.
I pretty much doubt it can be taken down at this point.