Tools I use, for personal and impersonal reference.
All safe, tested, and functional (at lease enough for me; use AdBlock, assuming you aren't already.)
Obviously support artists, but if necessary, piracy is preservation.

For Soundcloud: Soundcloud DL for Firefox
                Some blank artist names or characters stop it from working; if so, I use DownloadSound.cloud, and if that fails, then Klickaud.
                DownloadSound.cloud downloads playlists and liked tracks from users, too.
                Klickaud has no embedded metadata, so make sure to label your files right.
                For downloading art and PFPs:
                  Firefox allows you to open images (including profile pictures and banners) in a new tab. Chrome does not, but you can inspect element and get it anyway.
                  Replace "t500x500" or whatever in the URL with "original" to get the original size image.
For YouTube: EzMP3 (supports MP3 320kbps, pretty simple and safe)
             Obviously YouTube-DL is ideal but I'm too dumb to get it to work
             For thumbnails: https://youtube-thumbnail-grabber.com/
             For profile pictures: https://imageyoutube.com/profile-photo-download/
             For MP4: TubeMP4
For Mixcloud: Mixcloud Downloader
For screen recording: Audacity loopback (Windows WASAPI > Speakers (High Definition Audio Device) (loopback))
For Bandcamp: Bandcamp Downloader; bulk downloads entire pages, many useful options
              If that fails (unlikely,) Download Bandcamp (manual, no metadata)
              When downloading banners and profile pictures or backgrounds, replace the "_10" or whatever at the end with "_0"; it will load in the original file.
For image editing: Photopea
For Spotify: Spotify Music Downloader
For uploading YouTube videos: One Image Music Video
                              (Like Tunes2Tube, but without a watermark)
For bulk tagging or renaming files: Foobar2000 (Tagging > Manage Scripts; the Masstagger option is a lifesaver)
                                    It's really simple to use and saved me hours and hours of work.
                                    Manual tagging is easiest in Winamp, I think. Lets you go through lots of files quickly.
For file conversions: VLC  &  for splitting and editing files: Audacity

For finding interesting imagery:
    http://commons.wikimedia.org/wiki/Special:Random/File
    https://randomwaffle.gbs.fm/
    https://gifcities.org/
    https://thatclowngoddess.itch.io/met-oa-infinite-scroll
    https://archive.org/details/image
    https://archive.org/details/propix?page=2
    https://fragmentarium.ms/

Will update with time.