The Alphabit Synthesis Machine
The Alphabit Synthesis Machine is "an aid to explorers of the liminal territory between familiarity and chaos. An interactive Java applet, the Machine invites you to evolve the letterforms of a personalized "alien alphabet": the possible writing system of your own imaginary civilization."from the folks at PBS. After fiddling with your new alphabet's evolution, you can download it as a Truetype font.
PBS - The Alphabet Synthesis Machine (Introduction)