Flatpress-plugins is a project mainly written in PHP, it's free.
Plugins for flatpress.org blogging engine
A few plugins for flatpress.org blogging system.
livehelp: Adds javascript to load olark.com live help system. Edit source file to set your key.
sharethis: Adds bbcode tag to insert sharethis.com popup in your posts. Just use [sharethis=YOUR_PUBLISHER_KEY]