MUSIC

[DDL/App] Deezloader [app - FLAC/mp3] - Download songs from Deezer in 320kbps quality. You can convert your Spotify playlist to a Deezer playlist and download it via Deezloader as well.
[P2P/App] Soulseek [FLAC/ALAC/mp3/m4a] - P2P network used for music. Unlike bittorrent, the protocol used here is direct P2P i.e. downloading and uploading is not done with multiple users simultaneously but with a single user (like downloading a file from a website). This provides more security than public trackers as there is no swarm for copyright trolls to stay in and monitor. Unlike other sources (except youtube), there is no quality control though the chances of encountering low quality files is still quite low. For people wanting to share their libraries, soulseek is the easiest and fastest way.
[Torrents] rutracker.org [FLAC/ALAC/m4a/mp3] [.org, .net, .nl] - Russian tracker with an extensive music catalog.
[DDL] free-mp3-download.net [FLAC/mp3] - High quality music downloads. Uses only unintrusive banner ads.
[DDL/App] Youtube-dl - command-line program to download video/audio from Youtube videos and other sites.
- [DDL/App] Youtube-dl-GUI - GUI for youtube-dl for those not proficient in using the command line.
[DDL] Khinsider [mp3] - Original game soundtracks/scores.
[Streaming/DDL/Android App] Fildo [mp3] - music streaming and download.

[Semi-Private] en.metal-tracker.com - A very nice tracker for metal music.
Redacted.ch (RED) [FLAC /mp3] - Best music private tracker. One of the harder trackers to maintain ratio on.
Orpheus.network [FLAC/mp3] - 2nd best music private tracker, after RED. Much easier ratio economy compared to RED. In addition, there is a thread where you can request any torrent available on RED, without putting a request. This provides full access to RED without the hard economy. It is highly beneficial to have accounts on both trackers.