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.
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.
XML parser class is a PHP class that parses arbitrary XML input and builds an array with the structure of all tag and data elements. Optionally it can keep track of the positions of each element to locate elements that may be contextually in error. Supports a parsed file cache to minimize the overhead of parsing the same file repeatedly. Optimized parsing of simplified XML (SML) formats ignoring the tag attributes.
NetCrawler is the frontend to a Web crawling system. This command line application will download all of the pages within a domain, and then parse and process all of the relative content (Images, Text, Audio, Video), saving this content within an XML document for later processing. It is definitely alpha quality, but has been used quite extensively.