Learning resources

To facilitate selfstudy, the resources here are classified by target audience. However, if you get stuck, don't hesitate to request help in a chat room (APL Farm or APL Orchard) or ask a question on Stack Exchange.
It may be beneficial to learn the APL terminology.
For nonprogrammers
Some of the best resources for somebody new to APL and programming in general are:
In text form
 APL Wiki's simple examples
 The Learn tab on TryAPL
 The book Mastering Dyalog APL by Bernard Legrand
 The book APL2 at a Glance by Jim Brown, Sandra Pakin, and Ray Polivka (also in German)
 Learning APL with APLX (also as PDF)
 The Zark APL Tutor
 APL a Day: Introduction, Functions, Arrays, Values, Arrays have Shape
 A Practical Introduction to APL 1 & 2 (3 & 4 is for experts)
 MENACE in APL (An early Reinforcement Learning project reimplemented in APL)
 The tutorial from the old APL Wiki
Video series
 Découvrez le langage APL: parts 1, 2, 3 by Eric Schrafstetter (in French)
 Learn APL with neural networks
 APLtrainer tutorials
 Learn APL: Every single glyph! by Jeremy Howard
Follow one or a couple of these tutorials through and play around a bit. To learn APL the advice is similar to that for learning other languages: have a goal (something you want to accomplish) and try to do it. Along the way you are sure to come across the pitfalls and gotchas of the language, and with time you may come to understand what APL thinking means.
For programmers unfamiliar with APL
This is a list of tutorials and other resources of interest to someone who knows about programming or is familiar with another programming language, but wants to learn more about APL.
 APL Wiki's advanced examples
 APL Wiki's Books
 APL Wiki's Papers
 TryAPL online interpreter with lessons
 APL Workshop (selfstudy course)
 Learn X in Y minutes
 Let's Learn A Programming Language
 The book Mastering Dyalog APL by Bernard Legrand
 The book Learning APL by Stefan Kruger
 The book APL2 at a Glance by Jim Brown, Sandra Pakin, Ray Polivka (also in German)
 Zark tutorial
 Trying APL
 Learn APL with neural networks (video series)
 Artificial Neural Networks
 FizzBuzz
 APL deserves its renaissance too (interactive explanation of John Scholes' Conway's Game of Life)
 An Introduction to APL (video)
For novice APLers
 APL Cultivations by Adám Brudzewsky (edited by Stefan Kruger)
 APL Wiki's advanced examples
 APL2 in Depth by Norman Thomson and Ray Polivka
 Learn APL with neural networks (video series)
If you already have a fair grasp of APL's primitive functions and operators, you can sharpen your skills by challenging yourself with these:
 APLcart Quiz: Be challenged to write a function for a given task or to explain what a given function does. (Based on APLcart data.)
 2016 Year Game: Find APL expressions involving exactly the digits 2 0 1 6 in that order to equal the numbers 0 to 100.
 2017 Code Golf Challenge: Find the shortest possible APL expression that evaluates 1…52 without using any number or character literals.
 Previous years' problems from the APL Problem Solving Competition. Phase I problems are available with automated testing.
 APLeusis: A game for honing your ability to "think in APL".
 Advent of Code: A collection of small programming puzzles.
 Triplets pythagoriciens by OsKaR: A mathematical problem used as an introduction to the expressive power of APL (video series in French).
For advanced APLers
Here is a list of "howto"s on various subjects:
 Learn APL with neural networks (video series)
Haven't used APL in a while?
Those who learned APL "in the early days" should note that several implementations have made significant extensions to the language and system in the last decade or two.
 General video: Dyalog APL for other APL users (assignment, control structures, namespaces, migration level, Bind, userdefined operators, dfns, error trapping, shyness, namelists, GCD, LCM, Power operator, and more)
 New primitive functions:
⊢
Same, Right;⊣
Same, Left;⌷
Materialise, Index;≡
Depth, Match;≢
Tally, Not Match;≠
Nub Sieve;⍸
Where, Interval Index;⊆
Nest, Partition
 New primitive operators:
⍨
Commute, Constant;@
At;∘
Bind, Beside;⍤
Atop, Rank;⍥
Over;⍤
Rank;⌸
Key;⌺
Stencil;⍠
Variant;&
Spawn
 Lambdas (dfns): Intro; Details; Operators; The dfns workspace (collection of categorized utilities with extensive comments and notes)
 Tacit programming: Dyalog APL documentation: Intro; Details; short video; long video; APL Cultivation lesson; Function composition
 Other features and concepts: Keywords; Objectoriented programming; namespaces; Total array ordering; Leading axis theory; Complex numbers
APL development [edit]  

Interface  Session ∙ Typing glyphs (on Linux) ∙ Fonts ∙ Text editors 
Publications  Introductions ∙ Learning resources ∙ Simple examples ∙ Advanced examples ∙ Mnemonics ∙ Standards ∙ A Dictionary of APL ∙ Case studies ∙ Documentation suites ∙ Books ∙ Papers ∙ Videos ∙ Periodicals ∙ Terminology (Chinese, German) ∙ Neural networks ∙ Error trapping with Dyalog APL (in forms) 
Sharing code  Backwards compatibility ∙ APLcart ∙ APLTree ∙ APLCation ∙ Dfns workspace ∙ Tatin 
Implementation  Developers (APL2000, Dyalog, GNU APL community, IBM, IPSA, STSC) ∙ Resources ∙ Opensource ∙ Magic function ∙ Performance ∙ APL hardware 