Digital Invisible Ink Toolkit is a Java steganography tool that can
hide any sort of file inside a digital image (regarding that the
message will fit, and the image is 24 bit colour). There are four
highly customisable algorithms in the tool, as well as an open-source
implementation of RS Analysis (an extremely good steganalysis method).
The tool has the additional advantage of being able to simulate hiding
- so you can get an accurate map of where the information is hidden.