This is a general-purpose diary application that supports styled (unicode) text and images. Uses strong encryption to save its database (Blowfish). It works under Windows or Unix (Linux, or the BSD's), comes with full source code, and is released under the GNU copyright. (You might find some of the other software interesting, too --- like the Hieroglyphic word processor!)
I needed it for a novel in which the protagonist is studying Ancient Egyptian (so I could include samples of writing). It's a fascinating language, by the way --- and easier to learn than one might think.