Your desired plugins might be not available at WordPress.com. But, on Extra section at http://[your url].wordpress.com/wp-admin/themes.php?page=theme-extras their you will get two extra plugins. Currently they has two plugins and you can control both plugins within a click.
Below Name of Plugins and Works are given:
Uncheck The Box: If you uncheck plugins will not work for your sites.
Check The Box: If you check plugins – will work for your websites.
Don’t forget to press Updates Extras.
Enable Snap Shots on this blog: You’re working or talking with different topics and also linking up with different sites. When your reader move over to a active link – this plugins will show the information of Word (only active links) and without leaving you pages they get the idea of your topics. Just Snap Shots helps instantly otherwise – a reader might be open a dictionary or start to search on Google and they can motive or to start another one sites and shortly they can leave your websites.
Related Links Generator: You’re writing about WordPress.com and thousnads of people already wrote down about WordPress.com. If this Generator found relevenat information on web – in below of your posts it’s show the active links with post titles and thus you can know what other says.