A few days ago I was lurking around the Doomworld forums and found an interesting thread from reveilleun about floppy disks he found - filled with 1,44 MB of custom material. Linguica posted a very interesting thread about some more addon cds which are directly hosted at the archives.org with even more '94ish material that I found supercool as it retrieved a lot of memories from my childhood about exactly these addon cds. I am not sure if everyone else was aware about it so I thought it's a good idea to share it here as well.
I had a few floppies and CDs with Doom addons back in the day.... Most are lost now but I still have two CDs, one is called "Boom Powerpack" and has 440 Levels, new monsters and weapons and the other is called "The Ultimate Doom Techno" and has 100 Levels and a really nice audio track.
Here's the tune: