Infinite Jest by David Foster Wallace has been the most impactful, but due to the length of the book it's hard for others to compete on the impact-per-page metric. I wrote about it in detail here https://speak.sh/posts/infinite-jest
The Unbearable Lightness of Being by Milan Kundera showed me another perspective of love I had never considered. Gave me insight into vulnerability.
Flowers for Algernon by Daniel Keyes showed me how by looking through the world via a lens of intellect, you can often miss the point.
The Bus Driver Who Wanted To Be God by Etgar Keret a collection of some of my favourite short stories. Highly recommend.
I use Ping [0], never used an alternative so not sure how it compares on features, but it has everything I need: uptime alerts, header & body requests. All packaged in a nice interface with a solid pricing structure.
This resonates with me. Although I did not get into programming for money, I have come to hold the belief that I could make significantly more money as a programmer in a non-programming field. Money aside, the problems can take you far out of your comfort zone. I recently worked for a fashion start-up and the number of interesting problems that did not resemble at all what you are used to in the CRUD world was fascinating.
https://github.com/tomspeak/quiet-hacker-news -- the source is here, you could host your own version or run it locally on demand.