I am aware of full-blown content management systems (CMS) such as SugarCRM and TikiWiki... where content is typically stored in a database... and edited through the same interface as it is published. While I like many of the features, the product is clearly aimed at enterprise-wide use rather than to be public-facing.

What I'd like to establish are potential alternatives that fill the space between full-blown CMS and hand-coded bespoke site. I like the way that I can add modules to my CMS... allowing me to quickly introduce new functionality, and I'd like an analogous feature in a system for public web-content. Modules I know I'd like include moderated comments; web-form-to-email gateway; menus/tabs... in future, perhaps mapping or diaries or RSS integration - etc.

Where my requirements differ from a CMS, I don't need (or want) most content to be editable through the main site... and, somehow, I do want to be able to preview how updates will be presented to the public rather than to make live changes. For these purposes, in contrast to those where a typical CMS would be ideal, presentation is of paramount importance - and trumps any desire to immediately disseminate information.

I realise that this is a very high-level question... (suggestions of additional tags welcome) - I mentioned PHP only as - ideally - I'm looking for an open source solution and a PHP deployment is an easy option.

What are my options?