The Cutting Room Floor website (Announce)
„The Cutting Room Floor is a site dedicated to unearthing and researching unused and cut content from video games. From debug menus, to unused music, graphics, enemies, or levels, many games have content never meant to be seen by anybody but the developers — or even meant for everybody, but cut due to time/budget constraints.“
For instance, Category:DOS games has 427 pages from 3D Lemmings (DOS) to ZZT or Ész-kerék (Hungarian version of Wheel of Fortune)
And it's (partially) multi-language. 
I found this site via https://www.bamsoftware.com/software/exepack/, mentioned by ecm.
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