https://www.reddit.com/r/rational - a community about "rationalist" fiction, inspired by HPMOR. A lot of amazing authors and awesome stories, also cool discussion on related topics.

https://www.reddit.com/r/low_poly - a subreddit for 3d low-poly art. Really simple and beautiful artworks. You can easily get into voxel art with MagicaVoxel, or you can try Silo to model low-poly stuff.