Expandable is a project mainly written in PHP, it's free.
CakePHP Expandable Behavior
Add new Rows on the fly, without touching the database.
1.0.3
1.0.2
1.0.1
1.0
More Informations are located in german at my blog http://www.interaktionsdesigner.de/2011/02/11/cakephp-expandable-behavior/