I recently wrote tomlcheck, which, as the name implies, is a syntax checker for TOML files. Since I'd read a call-to-arms regarding the lack of concrete success stories in Haskell a few months ago, I figured I'd contribute one of mine.
If you were on the math team during high school, you may remember integer partitions not too fondly. They're not particularly easy to get a grip on: even counting the partitions of an integer requires generating functions (which are scary when you're in high school).
Aphorisms in Haskell, using only functions in base and with a particular bend
towards showing the use of lists for control flow. Many of these are adapted
from here.
A set of curated examples meant to show Haskell's expressiveness, wherein we write a sum function many times: