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.
mod_filter allows you to filter output from other modules inside of Apache. This allows you to implement filters (think Swedish Chef, jive, etc.). You can also use it to retailer output for your locale. This works with HTML documents, mod_perl, PHP, JServ, CGIs, and for that matter just about any sort of custom handler you might have.
The Perl Embedding Engine is a Perl-based template engine that allows embedded Perl code in HTML templates similar to PHP, JSP, etc. It is simple, flexible, and easy-to-use, and supports 2 modes of operation: offline generation and dynamic interpretation. Unlike many template engines, it only has 3 special tags so parsing is a breeze and it generates plain Perl code.
Safecat copies standard input to a qmail-style maildir as reliably and quickly as qmail itself. It can be used to deliver mail messages to qmail folders, or to spool data securely for later use by non-email-related applications. Safecat was originally written as a spooling utility for a CGI-based data collection application; it was inspired by the super-reliability of Dan Bernstein's maildir algorithm.
TkDVI is a DVI previewer built with the Tcl/Tk toolkit. It can use multiple windows to display multiple pages at the same time (which can come from multiple DVI files sharing a common font repository). Each window can show either a single page, two facing pages (as in a book) or sixteen reduced pages in the space of one, to check page breaks and positioning of floating items. TkDVI supports many features from xdvi, such as a magnification glass, but also adds interesting stuff like a gv-like page selector and a `rubber line' for measuring distances. TkDVI is based on a reusable Tk `image type' for DVI files which can easily be incorporated in other programs, and it is straightforward to customize and extend TkDVI itself.