It’s true that the greatest success for WordPress is the plugin development, in fact i think that it’s the plugin which make WordPress become so success, thanks to those plugin developers for their hardwork.
However, one bad thing about WordPress plugin is that until now there are still no place to collect all the WordPress plugin, or a database to put all the plugins so WordPress user will easily find the plugin they want, although there is wp-plugins.org but the lack of user interface and not up to date plugins make people would rather search plugins by them self.
Many works had already done to promote WordPress plugins though, such as daily plugin update by Weblog Tools Collection and A Month of WordPress Plugins by Lorelle where he spend the whole month talking and reviewing about WordPress plugins. These works will more or less promote WordPress plugins until a certain level but still we need a place that’s more particular and more general.
So if you are WordPress plugin developer, please add your plugin there, hopefully this will bring up all the WordPress plugins.