The following keywords are related to encoding mechanisms and specific codes. All alphabets are here.
25-pair color code
5-bit binary alphabet: see binary/biliteral/Baconian cipher
A=1, B=2, ...
A1Z26: see A=1, B=2, ...
airline codes
airport codes
alethiometer (golden compass from His Dark Materials)
amino acids
Anglo-American telegraph code
area codes
ASCII
Atbash cipher
autokey cipher
Ave Maria cipher
base 5
Baudot code
Beale cipher: see book code
Beaufort cipher
bifid cipher
binary/biliteral/Baconian cipher
bitwise OR
book cipher
book code
Braille
building 16-56 floor code
Caesar shifts
Chaocipher
Chromaphonoglyphics
Code 128
Colemak keyboard: see keyboard
Commander Keen alphabet
conlangs: see invented languages
country codes (any variety)
Cyrillic alphabet
Daedric alphabet (Elder Scrolls)
Dancing Men cipher
data matrix
Diceware
Dinotopia footprint alphabet
DNA, RNA
Dvorak keyboard: see keyboard
EBCDIC
elder futhark: see Futhorc
Enigma cipher
Fakoo
futhark: see Futhorc
Futhorc
Futurama alphabet
Gnommish alphabet (Artemis Fowl)
"The Gold Bug"
Graffiti (Palm Pilot writing)
Gray code
Gringmuth notation
hieroglyphics
homophonic substitution cipher
Huffman coding
ICD-10 codes for medical diagnoses
I Ching
Illinois driver's license code
Ingress glyph language
invented languages
ISBNs
keyboard
leetspeak
maritime signal flags
Matoran alphabet (Bionicle)
message encrypted multiple times
Moon type
Morse code
NATO alphabet: see phonetic alphabet
Navajo code talk
one-time pad, Gronsfeld cipher, or Augustus cipher
one time pad used multiple times
Phoenician alphabet
phone keypad
phonespell (2 = A,B,C)
phonetic alphabet
Pig Latin
pigpen cipher
Playfair square cipher
playing cards code (assigning letters to specific cards)
PLU codes
police alphabet: see phonetic alphabet
produce PLU codes
QR code
qwerty: see keyboard
rail fence cipher
resistor color code
ring sizes
ROT-13
RSA cipher
runes: see Futhorc
scytale
semaphore
shifting letters
shortlex order
Sign Language
Smithy code
Solitaire (encryption algorithm from Cryptonomicon)
steganography
T9: see phonespell (2 = A,B,C)
tap code
telephone exchange words (like 55 = Klondike)
ternary cipher
transposition cipher
Unicode
UPC barcodes
Vigenère cipher
ZIP codes