AFT (Almost Free Text) is a document preparation system. It is mostly free form, meaning that there is little intrusive markup; AFT source documents look a lot like plain old ASCII text. It has a few rules for structuring your document, more to do with formatting your text than embedding lots of commands, and it produces all types of output (HTML, XHTML, LaTeX, roll-your-own XML, etc.). All that needs to be done is to edit a rule file. You can even customize your own rule files for specialized output.
bkmrkconv will convert Netscape's bookmarks.html file into a series of interconnected HTML pages which can be put online. The pages are heavily customizable and examples are included for a Yahoo-like portal. The program is useful for accessing your bookmarks from a remote machine or even just for making your links look prettier.
FreeMarker is a template engine that was originally designed so that servlet-based applications could keep graphical design separate from application logic. The templates provide an easy and highly flexible way to generate any kind of text output (HTML, PostScript, TeX, source code, etc.) from a variety of data sources such as Java objects, Jython objects, XML object models, and more.
GPP is a general-purpose preprocessor with customizable syntax, suitable for a wide range of preprocessing tasks. Its independence from any programming language makes it much more versatile than cpp, while its syntax is lighter and more flexible than that of m4. The syntax is fully customizable, which makes it possible to process text files, HTML, or source code equally efficiently in a variety of languages.
HTML::Mason is a full-featured web site development and delivery system. Mason allows web pages and sites to be constructed from shared, reusable building blocks called components. Components contain a mix of Perl and HTML, and can call each other and pass values back and forth like subroutines. Components increase modularity and eliminate repetitive work. HTML::Mason is most powerful when used in conjunction with mod_perl, but can be used in standalone applications as well.