PHP Content Management System (phpCMS) makes it possible to need only one template for your whole Web site. It allows you to provide dynamic menus with unlimited levels, and use templates and sub-templates without a database. It is search engine-friendly and proxy-friendly, as the pages it generates can not be distinguished from static HTML pages. PHP code can be added to any template and content file with an optional module. It supports the caching of parsed pages and gzip compression.
Xapian is a search engine library, scalable to collections containing hundreds of millions of documents. It's written in C++ with bindings for Perl, Python, PHP, Java, Tcl, C#, Ruby, and Lua. It is a highly adaptable toolkit that allows developers to easily add advanced indexing and search facilities to their own applications. It supports the Probabilistic Information Retrieval model and also a rich set of boolean query operators. Omega is a Web search application built upon the Xapian library. It can index a Web server's document tree (including HTML, PDF, OpenOffice, MS Word/Excel/Powerpoint/Works, WordPerfect, RTF, PS, etc.), or data exported from arbitrary sources (e.g. SQL databases).
FXL Template an easy to use template engine offering all the basic features of a template system. It supports simple text/array assignments, blocks, and nested blocks. Well-used regular expressions and the simple template syntax are responsible for quick template processing. The template markup is quite easy to learn, even for those not into programming. A Memcache extension for high traffic pages is freely available.