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 one of the many chat rooms and forums 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:
Interactive
 The Learn tab on TryAPL
 The Zark APL Tutor
Books
 Mastering Dyalog APL by Bernard Legrand
 APL2 at a Glance by Jim Brown, Sandra Pakin, and Ray Polivka (also in German)
 Learning APL with APLX (also as PDF)
 MENACE in APL (early reinforcement learning project)
 A Practical Introduction to APL 1 & 2 (3 & 4 is for experts)
Text
 APL Wiki's simple examples
 APL a Day: Introduction, Functions, Arrays, Values, Arrays have Shape
 The tutorial from the old APL Wiki
Video series
 APL Quest 2016 by Adám Brudzewsky
 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. See also APL Wiki's lists of advanced examples, books, and papers. "Trying APL" has examples for all primitives.
Interactive
 TryAPL online interpreter with lessons
 Zark tutorial
 APL deserves its renaissance too (on John Scholes' Conway's Game of Life)
Text courses
 APL Workshop
 Learn X in Y minutes
 Let’s Learn A Programming Language, part 1, part 2, and FizzBuzz
 Artificial Neural Networks
Video
Books
 Mastering Dyalog APL by Bernard Legrand
 Learning APL by Stefan Kruger
 Getting started in APL by solving Project Euler problems 1 to 50 by Matthias Geiss
 APL2 at a Glance by Jim Brown, Sandra Pakin, Ray Polivka (also in German)
For novice APLers
Besides for APL Wiki's advanced examples, you can hone your APL skill with these materials.
Books
 APL Cultivations by Adám Brudzewsky (edited by Stefan Kruger)
 APL2 in Depth by Norman Thomson and Ray Polivka
 A Practical Introduction to APL 3 & 4
Video series
 Learn APL with neural networks
 Triplets pythagoriciens by OsKaR: A mathematical problem used as an introduction to the expressive power of APL (in French)
Challenges
 APL Exercises by Roger Hui
 APLcart Quiz: Be challenged to write a function for a given task or to explain what a given function does (based on APLcart data)
 APL Crosswords: 1 4 5 — Fill in expressions and snippets to fulfil all the clues
 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)
 Advent of Code: A collection of small programming puzzles
 APLeusis: A game for honing your ability to "think in APL"
For advanced APLers
Here is a list of "howto"s on various subjects:
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
 Dyalog APL for other APL users (video)
 Assignment
 Control structures
 Namespaces
 Migration level
 Userdefined operators
 Error trapping
 Shyness
 Namelists
 Keywords
 Objectoriented programming
 Total array ordering
 Leading axis theory
 Complex numbers
New primitive functions
 GCD and LCM
 Same (
⊢
and⊣
)  Materialise and Index (
⌷
)  Depth and Match (
≡
)  Tally and Not Match (
≢
)  Nub Sieve (
≠
)  Where and Interval Index (
⍸
)  Nest and Partition (
⊆
)
New primitive operators
 Power operator
 Commute and Constant (
⍨
)  At (
@
)  Bind and Beside (
∘
)  Atop and Rank (
⍤
)  Over (
⍥
)  Key (
⌸
)  Stencil (
⌺
)  Variant (
⍠
)  Spawn (
&
)
Lambdas (dfns)
 Intro
 Details
 Operators
 The dfns workspace (collection of categorized utilities with extensive comments and notes)
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 ∙ Cider 
Implementation  Developers (APL2000, Dyalog, GNU APL community, IBM, IPSA, STSC) ∙ Resources ∙ Opensource ∙ Magic function ∙ Performance ∙ APL hardware 