Some short essays which I think make for good use of reading time. The test for inclusion is whether I would've been happy to find the link from someone else's list. I highlighted in orange those that I think are particularly good, and in blue those that I felt stood out from the rest.
 The Relativity of Wrong (Isaac Asimov)

Mathematics on a Distant Planet (Richard Hamming)
 Related
 The Unreasonable Effectiveness of Mathematics (Richard Hamming)
 The Unreasonable Effectiveness of Mathematics in the Natural Sciences (Eugene Wigner)
 What Is Good Mathematics? (Terence Tao)
 Negative Probability (Richard Feynman)

The Inner Ring (C.S. Lewis)
 Related
 Machiavelli, Morals, and You (Martha Lagace / Joseph Badaracco)
 Cargo Cult Science (Richard Feynman)
 The Psychology of Human Misjudgment (Charlie Munger)
 Gospel of Wealth (Andrew Carnegie)
 Do Not Remain Nameless to Yourself (Richard Feynman)
 The Mundanity of Excellence (Daniel Chambliss)

You and Your Research (Richard Hamming)
 Related
 Advice to a Young Mathematician (Michael Atiyah)
 Advice For Graduate Students in Statistics (Michael Steele)
 Statistical Modeling: The Two Cultures (Leo Breiman)
 The Blind Men and the Elephant (as retold by John Saxe)

The Two Cultures of Mathematics (Timothy Gowers)
 Related
 PDE As a Unified Subject (Sergiu Klainerman)
 Structure and Randomness in Fourier Analysis and Number Theory (Terence Tao)

The Use of Knowledge in Society (Friedrich Hayek)
 Related
 Taking a Fence Down (G.K. Chesterton, in essence)

Warning Signs in Experimental Design and Interpretation (Peter Norvig)
 Related
 Ten Signs a Claimed Mathematical Breakthrough is Wrong (Scott Aaronson)
 20 Years, 20 Lessons, Part I (Part II) (Part III) (Mark Rosewater)

A Map of the Limits of Statistics (Nassim Taleb)
 Related
 Standard deviation (Nassim Taleb)
 A Philosophical Notebook (Nassim Taleb)
 Taste for Makers (Paul Graham)
 What You'll Wish You'd Known (Paul Graham)

Mathematical Problems (David Hilbert)
 Related
 Mathematics in the 20th Century (Michael Atiyah)
 How to Write Mathematics (Paul Hamos)
 Practical Thought About Practical Thought (Paraphrasing Charlie Munger)
 Unhappy Meals (Michael Pollan)
 The Strengths of the Academic Enterprise (Edsger Dijkstra)
 Craft in Operations Research (Hugh Miser)
 The Cryptographic Mathematics of Enigma (Ray Miller, NSA)
 The Future of Operational Research Is Past (Russell Ackoff)
 Negative Expertise (Marvin Minsky)
 The "No SelfDefeating Object" Argument (Terence Tao)
 The Importance of Stupidity in Scientific Research (Martin Schwartz)