The Lambda Calculus for Absolute Dummies (like myself) by Joscha Bach.
From the post:
If there is one highly underrated concept in philosophy today, it is computation. Why is it so important? Because computationalism is the new mechanism. For millennia, philosophers have struggled when they wanted to express or doubt that the universe can be explained in a mechanical way, because it is so difficult to explain what a machine is, and what it is not. The term computation does just this: it defines exactly what machines can do, and what not. If the universe/the mind/the brain/bunnies/God is explicable in a mechanical way, then it is a computer, and vice versa.
Unfortunately, most people outside of programming and computer science don’t know exactly what computation means. Many may have heard of Turing Machines, but these things tend to do more harm than good, because they leave strong intuitions of moving wheels and tapes, instead of what it really does: embodying the nature of computation.
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If you have ever struggled with the Lamda Calculus entry at Wikipedia, you will appreciate this well written introduction to the same subject.
I would re-title the post: Lamda Calculus by a Gifted Author.
I first heard about this post from Kirk Lowery.