This is for plugin developers,
I just finished developing a new API for calibre plugins that makes coding plugins a lot easier/cleaner. The new API is backward compatible, i.e. old plugins should continue to work. It also fixes a bug where some users on windows with non ASCII paths were unable to load plugins, however for this fix to work for your plugin, you have to move it to use the new API.
1. You can seamlessly import python code from different python files inside your plugin zip file using pythons normal import syntax, no more mucking around with zip import
2. A couple of new builtin functions that allow you to easy load images/data files from your plugin zip file
3. Point 1. means you no longer need the complicated structure of proxy classes in your InterfaceAction plugins
I also wrote a nice tutorial with sample plugins illustrating the techniques, available here: http://calibre-ebook.com/user_manual...g_plugins.html
Note that the example plugins have their minimum_calibre_version set to 0.7.53, so you either have to change the calibre version in your copy of the calibre source or wait for the next calibre release to actually run the plugins.
Let me know if you have any questions/concerns.