Think of it as a Wiki with only one page -- a single white (or whatever, use CSS) rectangle in which to jot notes, include drawings or pictures, even embed audio and video, using HTMLArea 3.0, a free in-browser WYSIWYG editor that works with Mozilla 1.4+ and Windows IE 5.5+

Use PHP to parse, process, and validate XML markup with the Simple API for XML (SAX) and Document Object Model (DOM)

Email marketing program written in PHP featuring multiple file attachments, SMTP servers, CCs, BCCs, HTML messages, and word wrap, and more. It can send email via sendmail, PHP mail(), or with SMTP. Methods are based on the popular AspEmail active server component.

Savant is a powerful but lightweight PEAR-compliant template system for PHP. It is non-compiling, and uses PHP itself as its template language so you don't need to learn a new markup system (c.f. comments and explanation from Harry Fuecks and Brian Lozier). It has an object-oriented system of template plugins and output filters, so it sports almost all of the power of Smarty with almost none of the overhead.