I really like the genre of short stories / novellas published by smart but amateur enthusiasts on the internet.
Here's a collection of some of my favorites. Note that the actual writing on a lot of them leaves a lot to be desired, but the core ideas are where the interesting stuff is.
I don't know, Timmy, being God is a big responsibility — simulated worlds
Three Worlds Collide — ethics, moral relativism, technological progress, levels of intelligence
The Metamorphosis of Prime Intellect — semi-aligned superintelligence, how to spend your time if you are forced to be immortal, but have godlike powers
A Casino Odyssey in Cyberspace — set in the Prime Intellect universe, this is a shorter story about how scarcity economics might still arise in an otherwise post-scarcity world
Let's Help Germinate This Seed — religion, creation, end-state of humanity
The Egg — religion, creation
The Last Question — end-state of humanity, not technically an "internet" fiction, since it's by Asimov, classic sci fi, but it fits in this list really well
The Last Answer — what to do with infinite time, also Asimov
Manna – Two Views of Humanity’s Future — near-ish future world in which AI and robots obviates human labor, how to cope, etc
Microcosmic God — genetic engineer super-intelligence, ethics, not technically internet fiction since it was written in 1941, but fits the vibe
I'll keep adding to this list as I find more stuff