AFAIK, there's no <del>framework</del> official/standard framework, and there will be as many plugin development styles as there are shades of white in north pole.

I'd say [WordPress Coding Standards](http://codex.wordpress.org/WordPress_Coding_Standards) are a blueprint for a good style.

You'll find **lots** of good examples and excellent coders here in WPSE. A nice starting point: [questions/tagged/plugin-development](http://wordpress.stackexchange.com/questions/tagged/plugin-development?sort=votes&pagesize=50).

Highlighting:

 - http://wordpress.stackexchange.com/q/715/12615
 - http://wordpress.stackexchange.com/q/7472/12615
 - http://wordpress.stackexchange.com/q/17903/12615

Nowadays, I use [Plugin Class Demo](https://gist.github.com/toscho/3804204) from [@toscho](http://wordpress.stackexchange.com/users/73/toscho) as base for many plugins.

Right now, [@Pippin](http://wordpress.stackexchange.com/users/2418/pippin) is doing a series [Introduction to WordPress Plugin Development 101](http://pippinsplugins.com/introduction-to-wordpress-plugin-development-101/) that may be of interest.

<i>[ **update**, thanks to [@Wyck](http://wordpress.stackexchange.com/users/1509/wyck) contribution, a list of helper-plugins/boilerplates/frameworks ]</i>

Plugin [***scbFramework***](http://wordpress.org/extend/plugins/scb-framework/), by [@scribu](http://wordpress.stackexchange.com/users/205/scribu):  
>A set of useful classes for faster plugin development.  
>This is a plugin toolkit that helps developers write plugins faster. It consists of several classes which handle common tasks, such as generating settings pages, creating database tables and more.

[***WordPress-Gear > PHP Boilerplate > Plugin stuff***](http://wpgear.org/)

1. [Plugin boilerplate][1] by @tommcfarlin
1. [Object Oriented Plugin Template][2]
1. [Settings framework][3] by @gilbitron
1. scbFramework - Classes for plugin dev
1. [WordPress Settings API][4] - by @tareq_cse
1. [WP MVC][5] - MVC framework to create plugins


  [1]: https://github.com/tommcfarlin/WordPress-Plugin-Boilerplate
  [2]: https://github.com/convissor/oop-plugin-template-solution
  [3]: https://github.com/gilbitron/WordPress-Settings-Framework
  [4]: https://github.com/tareq1988/wordpress-settings-api-class
  [5]: https://github.com/tombenner/wp-mvc