Hide and Seek (HideSeek)
From Just Solve the File Format Problem
Hide and Seek (HideSeek) by Colin Maroney is a steganography program that hides data in GIF files. It uses IDEA encryption with an optional 'key' (password). The author strongly recommends using gray-scale images as it's too obvious with color.
The Windows 95 version switches to BMP and Blowfish
Before v5.0 it was limited to 320x480 images and 19K of hidden data.