Revised Oct 2 2008:
Oct 19: added note about backup/restore

Sphider-Plus is the big brother of Sphider. I use the term "brother" in a loose sense. At this point, the code bases are so different that it's not clear what their relationship is. However, Sphider-Plus is definitely related and bigger. The overall size is over 5 times that of Sphider, although some of the difference is documentation.

Updated Oct 29 2008: added 68KB, now BSD

I am not sure why it took me this long to get around to CodeIgniter ... it's a worthy and mature PHP framework but I gravitated to CakePHP for some reason. Maybe it's the CodeIgniter licensing of EllisLab, Inc..

A nascent category for "associative" engines, neural networks and various statistical and connectionist approaches to inferencing.

Updated Sept 24 2008:

The Lanius website ( formerly known as the Drake CMS ) is up and running.

They have make some of their first production releases of the small, quick and generally admirable CMS, current version is Lanius v0.5.0 r580. [ wild cheers and celebration !!! ]

I'll install it and see ... stay tuned.

Updated Sept 24 2008: added features and SWCL link

Updated Sept 28 2008: fixups and links

From the CakePHP project site at ohloh.net:

Cake is a rapid development framework for PHP which uses commonly known design patterns like ActiveRecord, Association Data Mapping, Front Controller and MVC. Our primary goal is to provide a structured framework that enables PHP users at all levels to rapidly develop robust web applications, without any loss to flexibility.

Updated Oct 10 2008: added TWiki

There are several small, fast and powerful open source wikis that can be used as a full-featured CMS to for building small web sites and are fairly easy to extend and customize. Some may be capable of providing knowledge representation and management functions as well as the usual features available in traditional wikis. They may be the closest existing solution to some of the requirements for a Semantic Web ( however it gets defined ).

Updated Oct 2 2008: The Mission

There is a decided dearth of good PHP open source search engine solutions, but Sphider seems to be the leading candidate these days - "a lightweight web spider and search engine written in PHP, using MySQL as its back end database".

Updated: Sept 24 2008: more links, RAP

A very thin category at the moment, but the new Drupal Rules project may help to fill it out.

The RAP project has a simple forward and backward chaining inference engine using networks of relationships rather than condition/action statements like a true rule engine.

Update Nov 1 2008: ImpressCMS 1.1 released.

For most web applications, I assume PHP and mySQL as the CMS environment. Excluding big commercial C++ and Java systems, the ratio of PHP-based CMSs to all other languages combined must be at least four to one, maybe more. Slow perhaps, but PHP CMSs are easy to customize and virtually zero-configuration to deploy ( in sharp contrast to C++ and Java ).

Basic requirements for a small, general purpose CMS could be: