THE FIRST RULE ABOUT SLSK IS THAT YOU DON'T TALK ABOUT SLSK.
Soulseek is a P2P network and client that was originally started by a group of people on an IDM discussion list to give them a way to do something more than just talk about music and easily share said music.
The original slsk client is Windows only, but there is a linux port called pyslsk that uses Python. As such, the pyslsk client works for OS X if you can get Python running on it.
Soulseek is also a record label that publishes artists from the soulseek network.
Soulseek always has and always will be dedicated to the obscure, the eclectic, the bleepy, the noisy, the weird, the independent and the unobtainable. And I mean unobtainable. There are thousands of songs that you couldn't buy at any price, even if you really, really wanted to.
Besides the rare and limited release music that you couldn't find in even the most eclectic and independent record stores, besides the slightly rare stuff you could probably buy (at a price) from collectors, slsk is also a treasure trove of independent artists, bedroom noodlers, and musicological guerilla wacko fruitcakes that openly and freely share their own music, remixes, DJ sets and mash ups on the slsk network.
That being said, slsk is a music community unparalleled. Yeah, Napster was cool back in the day, but never this cool or this hip or this postmodern.
On my homenode down towards the bottom I list a bunch of music that I'm currently listening to. Some of it you'll likely recognize if you're into this stuff. Some of it you won't, even if you're total fanatic of electronic/experimental stuff. (This is not to say that I would recognize everything obscure that you may have. In this day and age, thankfully, it is impossible. Share. :) ) How do I find it? Slsk. Slsk is my silver bullet, my pocketed ace, my houris. Slsk is a DJ's best friend and wanton lover and demanding bitch, all rolled into one slick and sexy package.
How do you go about finding these unknown artists? You ask. You download stuff willy-nilly, whatever catches your eye. You listen to it. If it tickles your ear, you remember, and go get more. Slsk has an active community that you can communicate with through chatrooms, not entirely unlike Napster. Rooms are often labeled by genre, style, and various interests. Familiarize yourself with various known genres, and go a step further and learn about the stuff that belongs to emerging genres, or is entirely unclassifiable.
It is not uncommon that if you find something independent and "unpublished" that you like, and if you search for more of it and find a user with a bunch of it that you're now downloading it from the actual artist that produced the "unpublished" music in question. This is one of the things that sets slsk far above and beyond the realm of a normal P2P client and network. This is open source applied to music, and it is fantastic and wonderful. This is arguably the best use of slsk. This is the future of music.
Burn your idols, smash the altar to pieces, light your tired old guitar on fire and weep not for the future. We're all artists here. The line between the performer, the performed, and the audience is obliterated once and for all.
If you choose to use the slsk client, you should and should not do certain things to help protect the slsk network and community. Following these rules of thumb will protect both the integrity and quality of the slsk network. As far as I know and at last glance, the centralized slsk servers can handle a maximum of 100,000 users at once.
You should not share mainstream, RIAA member published crap. (Slsk users have been known to harass people who do. I did mention the musicological guerilla fruitcakes, right? I'm one of them. If I see Britney's Sphears or other crap in your shared folder you will get a nastygram from me.) You should not allow your client to share MPAA movies, licensed software, or other copyrighted material. You should not use slsk to search for and download these things either.
You should certainly share music that you've created, or have permission to distribute. You should share rare and obscure stuff, like Coil, Halfer Trio, Nurse with Wound, and stuff like that that falls into the realm of Unobtanium collector's material. You should share bootlegs and live recordings. You should seek out and actively participate in the music community at large and communicate with artists you would like to share. Ask the artist! In this realm, as I have emphasized so strongly, feedback and communication is valued. Some value it more than others. YMMV.
Feeling guilty about getting music for free? Search out the artists you've downloaded and send them money! Send them praise and feedback! Ask them if they're cool with having their stuff distributed! Communicate!
Please help protect and enhance the soulseek network. Slsk is incredibly unique and highly valuable in a world trending towards monoculture in all things, not just music and art. Slsk is like a library. Do you want to see it destroyed? Do you want to see the shelves stocked only with Dean Koontz paperbacks and cheap romance novels? Do your part and be conscious and aware of what you do. Slsk is not anonymous and protected in the decentralized manner that P2P systems like KaZaA and BitTorrent are.
And always remember, we're at war.
Where can you find slsk? The link in the above writeup is dead? I'm not going to post the current direct link to it here, sorry. Militant guerilla musicological wackos. You can find it. Try blogspot.