Resources
Here is a list of resources with a brief description of how they might be useful.
CyberChef - Useful for decoding, but it's a bit advanced and complicated.
ASCII Tabke - Each character (letter) on a computer is represented numerically. Here is a list.
TinEye Image Search - You're probably familiar with Google Images, but TinEye is much better for precise matches.
CrackStation - CrackStation uses massive pre-computed lookup tables to crack password hashes.
Cipher Identifier - This free tool will help you identify the type of encryption, as well as give you guidance about solving it and any available cipher decoder.
Decrypt a Message - Can be used to crack secret messages
Image Comparison Checker - Tool that helps you see differences in images.
TextCompare - Highlight differences in strings of text.
Caesar Cipher - Decode substituion ciphers.