Ever since WordPress version 2.6 you can actually move your wp-content directory to a different location. The wp-content directory will store all your theme files, plugin files and images.
Why Move The wp-content Folder
The best reason to move the wp-content is for security if you move this to an unexpected location any hackers looking to target this area won't be able to find it, or it will make it more difficult to find.
To change the location of the wp-content is quite simple as the location of this folder can be configured in your wp-config.php file.
All you have to do is add a new variable WP_CONTENT_DIR and change the location of your wp-content folder.
define( 'WP_CONTENT_DIR', $_SERVER['DOCUMENT_ROOT'] . '/blog/content/wp-content' );
To change the location of the wp-content URL there is another variable you can define in the wp-config.
define( 'WP_CONTENT_URL', 'http://www.paulund.co.uk/blog/content/wp-content' );
Moving Plugin Folder
If you don't want to change the location of the entire wp-content folder but just want to move the plugins folder then you can change this location the same as above.
For the plugin folder location we need to define the variable WP_PLUGIN_DIR.
define( 'WP_PLUGIN_DIR', $_SERVER['DOCUMENT_ROOT'] . '/blog/content/wp-content/plugins' );
The same as the wp-content folder you can change the URL of the plugin folder for the variable WP_PLUGIN_URL.
define( 'WP_PLUGIN_URL', 'http://example/blog/content/wp-content/plugins');
The problem with doing this for plugins is that there is another variable which can be used by some plugin developers...PLUGINDIR. Therefore you need to make sure that you change this too.
define( 'PLUGINDIR', $_SERVER['DOCUMENT_ROOT'] . '/blog/content/wp-content/plugins' );