WP Plugin Info is a WordPress plugin by _luigi that lets you show, in a post or page, any kind of information related to a plugin hosted on WordPress.org. I developed it for my own use on sitetreeplugin.com, the information you see in the sidebar are fetched with this plugin.
Shortcode-based plugin: you just need the shortcode [wp-plugin-info] to use it.
The information retrieved are cached and refreshed once per hour. It is able to efficiently manage the caching of multiple arrays of the information (each one related to a different plugin) at the same time.
Optimised performances: even if you insert the shortcode multiple times into the same page, the access to the cached data will be performed just once.
Download and info: http://wordpress.org/extend/plugins/wp-plugin-info/