AutoTOC is a project mainly written in PHP, it's free.
Generates Table Of Contents based on HTML headings in page
This Cotonti plugin automatically generates a Table Of Contents for any page. HTML heading tags are extracted and listed in a tree. The page body is modified to include anchors between the TOC and the headings.
Simply upload the plugin folder to your /plugins directory and enable the plugin in your Administration panel.
The plugin has one configurable setting. You can configure the HTML tags that should be included in the TOC. Default value is h2,h3.