The Printable Puzzle Project is a curated catalog of 3D printable puzzle models by a variety of puzzle designers. All our puzzles are modeled to high quality standards, fully tested, and open source. The puzzle designs are licensed for personal, non-commercial use only.

You can read more about the project here:
https://www.puzzlehub.org/ppp

If you're looking for recommendations on what to print first, check out our recommendations page:
https://www.puzzlehub.org/puzzles/suggested-puzzles