Pyblosxom is a weblog engine that uses standard text files located on your filesystem as a database of weblog entries. The concept is simple, managing content is as easy as editing a text file with your favorite text editor.
Pyblosxom is now hosted on http://pyblosxom.github.io/
CrystalNight is a web-based CGI game engine for a genre of game best described as "breeding" game. Meaning you, breed/train monsters/animals/etc. This is a game engine so the specifics for any game using it would need to be defined in the database.
Frosttie (FROnt-end SchemaTron Text Internet Engine) takes XHTML pages and processes them with various user-definable filters such a W3C's WAI, Section 508 (US) web usability compliance, ad removal, etc. It can be used with zKnowMan.