• flickrRSS - Allows you to integrate the photos from a flickr rss feed into your site. By Dave Kellam.
  

• Get Recent Comment - Display the most recent comments or trackbacks with your own formatting in the sidebar. Visit Options/Recent Comments after activation of the plugin. By Krischan Jodies.
  

• Extended Live Archives - Implements a dynamic archive, inspired by Binary Bonsai and the original Super Archives by Jonas Rabbe. Visit the ELA option panel to initialize the plugin. By Arnaud Froment.

• Gravatar - This plugin allows you to generate a gravatar URL complete with rating, size, default, and border options. See the documentation for syntax and usage. By Tom Werner.
  

• Most Popular Posts - Popular posts By Nathan Moinvaziri.
  

• Noteworthy - Mark posts as ‘noteworthy’. By Jamie Saunders.

• Quoter - Allows commenters to quote other comments (dynamically or server side if they have Javascript disabled) and any other text in a page (Javascript only). By Daniele Mancino.
  

• Related Posts - Returns a list of the related entries based on active/passive keyword matches. By Alexander Malov, Mike Lu & Jon Bourne.

• Scrobbler - Displays AudioScrobbler / Last.fm webservice information (e.g. recently played tracks), on your blog using AJAXrefreshing(tm) By Florian Kriener.
  

• SparkStats - Generates a Sparkline bar graph of your site posts and comments statistics. By Sean McBride
  

• Ultimate Tag Warrior - Ultimate Tag Warrior is a tagging plugin, that’s heavy on tag visualisation. I Like Pi!
  

• Yahoo/MSN Style Smileys - Displays Yahoo Messenger or MSN Messenger style smileys. Please deactivate ‘Convert emoticons like and to graphics on display’ under Writing Options menu when using this. By Priyadi Iman Nurcahyo.

• Make sure you are running WordPress 2.0+.
• Download the latest version of plainbox above.
• Upload the plainbox folder to wp-content/themes/ on your server.
• In your WordPress administration, go to Presentation and activate plainbox.

That’s it. You’ll find the options panel as a tab called ‘K2 Options’ in the Presentation section of the WordPress administration. After you’re up and running with plainbox, you can plug in whatever extra functionality you might want.