Caesum's Stego Guide - Caesum's Handbook has tons of great resources for CTF challanges and one of the best Stego guides around.
outguess - OutGuess is a universal tool for steganography that allows the insertion of hidden information into the redundant bits of data sources.
snowdrop - Snowdrop provides reliable, difficult to remove steganographic watermarking of text documents and C sources
steghide - Steghide is steganography program which hides bits of a data file in some of the least significant bits of another file in such a way that the existence of the data file is not visible and cannot be proven.
stegsnow - This utility can conceal messages in ASCII text by appending whitespaces to the end of lines. Because spaces and tabs are generally not visible in text viewers, the message is effectively hidden from casual observers. And if the built-in encryption is used, the message cannot be read even if it is detected.
Forensically - An amazing online tool that can provide different levels of photographic analysis on an image.
Asperisolve - Aperi'Solve is an online platform which performs layer analysis on image. The platform also uses zsteg, steghide, outguess, exiftool, binwalk, foremost and strings for deeper steganography analysis.