Sample-php is a project mainly written in ..., it's free.
sample php 10gen application
Several sample sites using PHP on 10gen.
The "basic" site is meant as a proof of concept of a PHP site running on 10gen. It also contains some tests showing various functionalities of 10gen's PHP support. Implementations of tutorials for PHP are forthcoming.
Then "student" site is a PHP implemention of the student web app, it is currently incomplete but is being actively worked on.
Tutorial documentation can also be reached from our main developer documentation page, here: http://www.10gen.com/wiki/DevDocumentation