The Hidden Palace is a videogames preservation group that has been active for a long time, their work focused more on things like pre-release builds, source codes and artwork.
With the help of an unnamed individual, the Internet Archive and more people in the community, a massive collection of pre-release PlayStation 2 game builds called Project Deluge has been released for public viewing.
Preservation Group The Hidden Palace Drops Project Deluge: Over 700 PS2 Prototypes
Project Deluge is still a work in progress. This list of software dumps comprises over 700 unique builds, from E3 demos to alpha builds and everything in-between. These are all downloadable and “playable” with the proper tools, letting anyone interested dive into various points of PlayStation 2 history.
This has been a long time coming, and the Hidden Palace website goes into tremendous details on how it all came together. This process involved diving into a massive, private collection, making dumps and analyzing content to compare it to retail releases. Final builds were a part of all this data, but once verified they were left out.
The folks at Hidden Palace stated this collection of 700 builds is just a portion of everything the team is organizing. The team compared this effort to an earlier one, a collection of over 1,000 Sega prototypes released back in 2008.
If you want to check out the list and see what kinds of game builds were found, you can check out the initial list here. Context is included, such as the build dates versus final release dates.