Drupal ExtJS4 (Sencha) integration
There is just a module that integrates Ext in Drupal that I know of: the Ext module.


  Loads the Ext JavaScript library (version 2.2 &amp; 2.3 for now) with Drupal. Other modules requiring Ext may use this module as a basis, or it may run on its own, simply loading the Ext library.
  
  Note: A new version of this module is being developed to provide relatively comprehensive integration functions with Ext 4.x (currently 4.1). For details please see http://drupal.org/node/1316616.


The module doesn't have a version for Drupal 7, though.