What is the skeleton structure for a Drupal 7 module?
Minimum files needed:

Normally, the minimum files needed for a module is the following: 

sites/all/modules/{name of your module}


{your module}.info 
{your module}.module


Or use the examples module:

The examples module on drupal.org provides you skeleton modules to develop custom/contrib modules. Just use that to copy and create your modules off of.

Check out the project page:


  This project aims to provide high-quality, well-documented API
  examples for a broad range of Drupal core functionality.
  
  (Interested in other, non-core examples?)
  
  Developers can learn how to use a particular API quickly by
  experimenting with the examples, and adapt them for their own use.


Link to the git repository: http://drupalcode.org/project/examples.git/tree/refs/heads/7.x-1.x

Code from the examples module:

I've also just pasted in the code you could get from the examples module.

example.info file:

name = Examples For Developers
description = A variety of example code for you to learn from and hack upon.
package = Example modules
core = 7.x


example.module file:

&lt;?php

/**
 * @file
 * This file serves as a stub file for the many Examples modules in the
 * @link http://drupal.org/project/examples Examples for Developers Project @endlink
 * which you can download and experiment with.
 *
 * One might say that examples.module is an example of documentation. However,
 * note that the example submodules define many doxygen groups, which may or
 * may not be a good strategy for other modules.
 */

/**
 * @defgroup examples Examples
 * @{
 * Well-documented API examples for a broad range of Drupal 7 core functionality.
 *
 * Developers can learn how to use a particular API quickly by experimenting
 * with the examples, and adapt them for their own use.
 *
 * Download the Examples for Developers Project (and participate with
 * submissions, bug reports, patches, and documentation) at
 * http://drupal.org/project/examples
 */

/**
 * Implements hook_help().
 */
function examples_help($path, $arg) {
  // re: http://drupal.org/node/767204
  // 5. We need a master group (Examples) that will be in a main
  // examples.module.
  // The examples.module should be mostly doxy comments that point to the other
  // examples.  It will also have a hook_help() explaining its purpose and how
  // to access the other examples.
}

/**
 * @} End of 'defgroup examples'.
 */