Links:

Cryptii – A very cool and very fast “modular” decryption tool that lets you run a string of text through several encryption/decryption methods of your choice.

The Black Chamber – A great collection of interactive tools that explain and allow you to decrypt a variety of common (and some uncommon) encoding schemes.

Decode Ingress – A list of tools that can help you with decoding  passcodes, originally provided for use with the AR game Ingress. Tools for text manipulating, basic conversions like text to ASCII, HEX to Base64. Tools to decipher Morse code.  Good Image exif info grabbers, and image editing tools for Steganography puzzles (messages hidden in digital images). A range of great info and tools about various ciphers, and their implementations.

Tools for Noobs: Online Decryption Tool – Decrypts a string using various algorithms (e.g. Blowfish, DES, TripleDES, Enigma).

Rumkin Deciphering Tools – This is a page dedicated to simple text manipulation tools, which all can be replicated with just paper and pencil. An amazing resource for deciphering methods, including many that we will definitely encounter in NCL puzzles (Atbash, Railfence and Vigenere).

MD5hashing.net Encryption and Decryption – At md5hashing.net you can hash (encrypt) any string into 66 different hash types. As you probably know – decryption of any hash is impossible, but they offer reverse decryption via our database (~1000M records, and counting).

Splitbrain.org Encoding/Decoding Tools – This tool helps you to quickly run some text through various different encoding/decoding functions available in PHP. Great for a lot of different decoding possibilities rapidly

CodeBeautify.org Encryption/Decryption Tool – A nice, clean tool for decrypting codes that you know the key for, or encrypting codes with your own original key.

SQLite Viewer for Chrome – Chrome plugin for viewing SQLite databases in your browser. Allows opening and editing of SQLite databases without requiring admin access to install.