Below are some tools that can be used to decode/encode, they are ordered alphabetically to make them easier to find.
Affine
ADFGVX
ADFGX
Atbash
Baconian
Beaufort
Caeser
Playfair
Polybius
Porta
Rail-fence
ROT13
Simple Substitution
Vigenère
This list is maintained by MysticKnight, If you find a useful tool that isn’t listed here and would like it added please email.