Word lists
The whole dictionary, sliced the ways that are actually useful. Every list shows real counts and real Scrabble scores, and every word links through to everything else its letters can make. Nothing here is a stub: if a list exists, it has the words in it.
By length
The most-used slice, and the one that says most about the games. There are only 96 two-letter words to learn and more than 28,000 at eight letters.
Starting with
Useful when there is a letter on the board and a free square in front of it. S leads the alphabet by a long way, which is true of almost every English dictionary.
Ending with
More practically useful than the beginnings, because a crossing answer usually confirms the last letter of a word before the first. S dominates again, for the obvious reason.
Common endings
Learn these and you stop reading your rack as seven loose letters. A large share of bonus words is a short stem plus one of these, and the same handful accounts for most long crossword answers.
Common prefixes
Less valuable than endings, because a prefix needs empty squares to the left of where you are building, while an ending can hook onto a letter already played. Still worth knowing for crosswords.
The two lists worth learning completely
All 107 two-letter words, because they are how points get squeezed out of a crowded board.
The 21 Q words with no U, because a Q you cannot play costs you both ten points and a turn.
Curiosities that are also useful
Words with no consonants are what rescue a rack of nothing but vowels, which is the most common bad draw in the game.
Words with no vowels look like typing accidents and are all perfectly legal.
Or start from your own letters
Lists are for browsing. If you have specific tiles in front of you, the solvers are faster.